I feel like I am losing grip on reality

I feel lost. Like I'm on a downward spiral. This last year my fiancé and father to my child took a break after I started going downhill. I stopped caring about everything. Started doing drugs I had always been against, drinking like crazy days in a row. Just to numb myself and take reality away. We currently got back together and I thought things would be better. That I would better myself but instead I feel empty inside. No one knows I did drugs or that I am currently doing them not all the time but like I said I was always against them so even once a month is a lot for me. Today I found out while my fiancé and I were split he slept with people. I can't hate him for his choices when we weren't together I did the same. But I can't help but be hurt and it's not fair to him I know this. I have had thoughts of hurting myself before this and am now currently having them. It's as if I could disappear and everything would just move forward. I don't even have the fear like I used to when I thought this way. I sat in the tub today just looking at my wrists and legs thinking of feeling the pain and watching the tub turn red. Then it would be over. I didn't have anything in the bathroom but I thought about going into the other one and getting something I could use. Then my mood passed. And came back when I was laying in bed but instead I just held my breath and my body just let me. I was almost to the point of blacking out when my fiancé rolled over he didn't have a clue and I kept it that way. I have no one to talk to and I am scared to take pills from the doctor to just be happy. I am having uncontrollable mood swings crying, and yelling because my mind won't turn off. Then I get sad and go through the same cycle. I went for a drive after the bed situation just to find myself thinking about driving my truck into a tree. I took the first step and told my fiancé how I was feeling and he reassured me but then my next mood swing hit and he got angry and told me I was a coward. That he would be sure to tell my daughter. Maybe that was his way to sway me but instead it made me fall even more. I feel so detached from myself and I'm so tired of going through this. I went through this when I was a teenager, after I had my daughter, again when she was two, again when she was 4, when my fiancé and I split up 8 months ago, and now again. I don't have people to turn to. My fiancé s friends and family treat me bad. My mom ditched out a couple years ago and my dad isn't really around. The friends I do have aren't there for me in this type of way and my fiancé is so up and down and I can't get out what I need to say when I don't understand it myself so he just gets angry with me and I feel worse. I'm alone and feel worthless. I know people will tell me I'm not if I tell them this but it won't make me feel any different. it's hard for me to think about my life and the struggle I have pulled through from being molested, multiple parents coming and then throwing me away like a piece of trash to getting pregnant in my teens with my now fiancé and the emotional and physical abuse we put each other through, to him doing drugs and cheating. (I know he sounds awful and that's not my intension) he grew up and try's his best with me. we don't abuse each other anymore, he is dedicated to me, takes care of our family, is clean from drugs. Our communication is lacking and why I feel like I have no one to talk to. Even if I had him maybe that would be enough but it doesn't work that way. Like I said previous how can he understand when I don't even understand. I'm sorry this was so long but I just wrote what I felt and I haven't been able to actually express myself fully even here. There is still so many more underlying things going on but I doubt anyone will read this one anyways just hoping it will make me feel better to tell someone... Anyone really