Fallen in love with my flatmate?

Hi, I think I may have fallen in love with my flatmate. Quick breakdown, I am 29, I've been widowed for 5 months and have a mental illness. My flatmate is 36, has never had a relationship longer than a few weeks and is drug and alcohol dependent. We've been friends for 4 years, and following my release from hospital 2 months ago have been living and working together. About 5 weeks ago we had a really scary experience at home and my flatmate offered to sleep in my room overnight. We cuddled, it was great, in the morning however we had sex. IT WAS FANTASTIC! We both agreed that no relationship should be formed outside the "friends with benefits" bracket as we are both too screwed up for anything long term. He is still my best friend and so protective of me, kind and sweet, everything you can want from a friend. However until 6 days ago we have shared a bed every night and had sex at least twice a day. 2 weeks ago he told me he loved me, and I've noticed he's started referring to me as his "girlfriend", to his mates and family. I've found I don't care, in fact I like it. I warned him I was falling in love with him, and he just shrugged, "we are both single adults, who cares" he replied. 6 days ago I went away for 16 days working abroad, on our last night together a friend of a friend propositioned me, to test my flatmate, I told the guy to ask my flatmates permission, my flatmate told the other guy to bugger off as I belonged to him. So I came away unsure whether I'm single or not? My flatmate tried everything to come on this trip with me, but work commitment meant we couldn't both be away at the same time on short notice. But I miss him, and I know he misses me. He has called everyday, even though I asked him not too as I pay the phone bill lol. I in return have written to him everyday, long rambling notes that have nothing to do with work or home. I have started finishing my letters with I love you. The problem is I know I am on the rebound, I miss my husband so very very much, and although I genuinely love my flatmate, I know a relationship with someone dependent on drugs and alcohol is not a sensible thing to do, or for him to get involve with a woman with a mental illness. I really don't want to stop sleeping with him, or living with him, nor kisses and cuddles and spending time etc, but I don't want us to hurt each other. All advice is gratefully received.

It really does sound mostly harmless, but you know that in the long term, it's not going to work out if you both aren't getting well in the long term. If you are interested in taking it further than what you have now, and want a more stable relationship, think about how you would like to improve as a person and overcome your heartbreak from your husband as well as take care of your mental illness. If you feel like your heart is in this place, as him about what his plans are for overcoming his drug and alcohol problems. If he seems just as motivated as you may be about getting better, you might be onto something more substantial. It's possible for two dysfunctional people who are geared towards making life better and breaking through to be a source of solace and a tool for positive transformation - as long as you are both set on making your lives better, you can soar through anything. This is not to give you false hope; this is what happens if you are set on making it through these problems. If you don't have those positive mindsets, you'll drag each other down; if one of you have a positive mindset and the other is stuck in their ways, the stubborn one drags down anyone that tries to stick by their side. If you both aren't willing to change right now, I guess it could still work out, but I can't say I'm sure it wouldn't have some nasty bumps with the problems you guys are dealing with individually. Take into consideration that being around an addict at this vulnerable time may cause you to befall heir fate. (I'm lucky I didn't make that happen with my ex.) If you feel like this isn't right to continue.. and worry that his behavior will only make you worse.. you may want to consider breaking it off and living somewhere else instead. wishing you the best and I hope this helps.