My (26F) fiancee has stopped showing any and all affection towards me (27M) what should I do?

For context we met back in high school and were good friends, after high school didn't talk for about 6 years. Ended up reconnecting and have been together for 3 years. During that time I've been supporting her since she has not worked, I've bought her countless gifts, bought her a car, I pay for all of her needs and I just recently bought a house for us. We've had our issues here and there (what couple doesnt) but we've always been able to move past it. But one day a month or so back it's like she woke up being a different person. She told me it's a "hard month" for her and that she's working on herself. She has gained weight and had a few mental health issues in the last few years and it seems she blames me for this and resents me for it even though I always tell her how beautiful she is and how much I love her. I still do all the little things (opening doors for her, complimenting her, showing affection, buying nice dinners, and grabbing her favorite things from the store to try and cheer her up) but she has been distant. She doesn't show me any affection, whenever she's on her games and I try to talk to her she makes me feel like I'm intruding and quickly dismisses me, we haven't had sex in months, she recoils from my touch, and shows absolutely zero affection or attention. She says she still loves me but it feels like she's not in love with me. She talks to lots of guys on her games and giggles and uses her cute voice but as soon as I get her attention it's like I'm an annoyance. I don't want to lose her but I don't know what to do anymore. All I do is try and it seems like none of it matters, it's gotten to the point I've become depressed and started drinking heavily and smoking cigarettes again after a year of quitting just to numb how I feel.