I really need HELP! asap

Okay, first off I’m 18. so I’ve been dating this guy Patrick for almost 2 years, and I love him more than anything. He was my oldest brothers best friend, and I fell in love with him. For the first year of our relationship it was perfect. I know theres that honeymoon stage or whatever but this was more than that. Everything was in place and we were both ourselves, it was a healthy relationship.

Last Febuary my brother died young and unexpectedly. We were all devastated, and Patrick was there every day for me, which i was so thankful of. He realized this thing i do with my eyes and looked it up and we discovered i have epilepsy and those eye movements were seizures. I got on medicine for it, and it made me angrier and more emotional. I am definitely not the same person i used to be, and who i really am. Ever since then our relationship has gone downhill. We had sex in March, and it was the first time for both of us. I love him more than anything, despite my age, but he is flirty and talks to other girls. When i confront him about it i know i do it the wrong way, and i get very angry, and i think its due to the medicine i take, and the grieving process.

We got in an argument and then a few days later he told me that he was having doubts about us, and that we had problems and it needed to change. The next day he went back to visit family for Christmas and ended up holding hands with this girl who he barely knew. Right after it happened he told me about it and how he was so sorry and how he knew I was going to be mad but he really loved me and it really opened his eyes on how important I was to him. Of course I was mad but I didnt have much room to talk, because a few months after my brother died i was talking to this guy and we ended up hanging out at a friends unexpectedly and he tried holding my hand and rubbing my leg. i let it happen and then i started to think about patrick and how messed up this situation was and i told him to leave. What bothers me the most about him holding hands with that girl is that he didnt stop it, even though it was like for 30 minutes roughly. When he was gone I started trying to improve myself and trust him more, and i was doing a good job until i found out about that girl. since he came home it wasnt as fun as when we hungout before, and it has started getting better. Last night he hung out with a bunch of friends that were in this “group” who involved his ex, who i dont like due to the fact she used to date him, she was physically abusive to him, and shes not nice to me. They all went to dinner and i didnt have a problem with it, but then his ex, and her friend who patrick has known since 1st grade who is also my brother who had passed away’s girlfriend, and one of their other guy friends. i know he doesnt like the stuff she does but has decided to put it aside and be neutral. I dont know, i just bothers me. And last night was the first time we have had an argument since he addressed somthing needed to change. I think its good considering we used to argue almost 3 times a week, and it shows we are making progress. Since he came back from virginia we decided no more sex, and to work on the best friend aspect of our relationship. We were doing good until last night and my attitude got the best of me. He ended up saying I dont care anymore, do what you want. This isnt going anywhere (obviously talking about our relationship). I told him no and stuff and we kinda worked things out, and he ended up saying he thinks im too serious about him. That hit me and put a bunch of questions in my head like if he still loves me and wants a future for us. but still i know i have things i need to work on. but it doesnt help when hes talking to these girls that he used to like, and is getting kinda flirty with them.

i know if i work on things everything could turn around and it could be like how we used to be. I need help on dealing with this, and i think the medicine i take plays into my anger, and im not the same as i used to be. the thing about my medicine is that it works great for me, but it makes my emotions crazy. So i dont know if i want to mess around with other medicines when this one is working good. I need some help on learning how to trust him and how to fix our relationship. weve gone through alot and we both know we would rather be with eachother than without, but if we are going to be with eachother things have to change. thats where i need some advice on things to do. ive tried talking about it to him like not talking to girls but he things im being controlling, when thats not my intentions.

anyways. help please? any advice on how to make this better and control my anger?