Long term relationship - Partner is closet bi

My background story is very, very long but I will simplify and shorten for the purpose of this post. My partner and I have been together for four years, in the first 8 months of dating I did come across a message from another male that was questionable and confronted my partner in regards to his sexuality. At this stage my partner brushed it off as banter, and a joke between him and a mate. I accepted this explanation and since have never thought twice about it. However, three years on and I have recently discovered that he has an active Grindr account, I did not find this out by snooping or invading his privacy, I simply saw him swiping through his apps and was interested in knowing what this app was. Upon discovering what it actually was, I became concerned and decided to download the app myself! Heres where I guess I have invaded privacy. I found his account, he is a regular user and not simply using the account to talk to other closet Bi's. He is actively looking for hook ups, (of which nature I am unsure), however now I feel betrayed that he has abused the trust I placed on our relationship, but keeping such a large secret. Knowing he is Bi does not change the way I feel about him. However, knowing he is BI and choosing to seek and explore alternative relationships unbeknownst to me, is quite heartbreaking. MY partner can be depressed and I know he would be extremely anxious about this getting out to anyone, including me. I don't want to confront him as his reaction may be unpredictable, however, what should I do? What could I do? I'm worried that he may be exposing me to danger (we are sexually active quite regularly but without protection) how am I to know he is clean and safe with others? How do I know he hasn't been doing this for an extensive period of time and may have already put me in danger? I would love to work through this with him, but I feel like he may cut me out completely if he finds out that I know. I don't want to leave him, but I don't want to continue this relationship the way it is, we built this relationship with trust and commitment and I feel like it has all been a lie on his part. IS he living the life he thinks he should live? Is it a cover up for what he actually wants? I need nonjudgmental advice and support! Please help.

There's only one sensible option here: Confront him! As you know, Grindr is aimed at gay and bisexual men and is designed to help them meet like-minded men in their area, most people would agree it's so men can meet for sex. There's nothing wrong with that, between consenting adults, but not when one of them is in a four year relationship where both are supposedly heterosexual. Firstly, there's no evidence he's done anything with other men, he could literally be confused and not even know himself if he's bisexual or not. In my opinion, that is very unlikely, because there are far more discreet and sensible ways to research your bisexual thoughts than be an active member of Grindr! If he just wants friends, why Grindr? It is natural for you to worry about STDs and you would be sensible to get tested right away and refuse to have sex with your boyfriend until you know what his game is. I'm not being discriminatory when I say there is a real risk of HIV here, even if it is a very minimal risk, but there are STDs you can contract whilst using a condom. This man has been dishonest which ever way you look at it. Four years together, potentially being bi the whole time and not telling you, whether he's had sexual contact with other men or not. He can't say he's on Grindr for the banter! Worst case scenario, he has been meeting men throughout the whole relationship. Cheating is cheating, even if you're confused about your sexuality. If it was me, I would want to know right now and given the potential worst-case scenario, you shouldn't hold back because of his feelings. Has he considered your feelings whilst being active on Grindr? If he claims innocence and you believe him, I'd still ask him to get tested for STDs. If he is innocent and loves you as he should, he should understand why you'd be worried about that.

Is it disrespectful to myself to feel like I have invested so much in to this relationship its worth tossing up the pros and the cons of confronting him? I honestly don't even know how he will respond. I do believe that I deserve the honesty and explanation, as I have always believed our relationship was built on trust. However, I do care for him so deeply, and I hate that he has to keep this a secret. I think I love him so so much that I am finding it difficult to rock the boat, even though I know this secret is eating me alive and a future in this situation is very flawed. Knowing what I know doesn't even change the way I feel about him, it simply makes me want to know how he truly feels about me, and whether I am simply the mask he wears in order to participate in a world he believes is easier to live in. If I have been exposed to HIV, this opens up a whole new scenario. I need to muster up the strength to deal with all of this, and I don't even know where to start.