my relationship is in danger

My gf and i have been together for about a year and a half now and its every other day we fight sometimes minimal sometimes an all out war. we are both bi polar and both blame each other for the fighting i think its her she thinks its me. the main problem i have is that when we're good its the best time of my life but when we're bad its the worst my friends tell me to leave her that its not worth it but i love her to death. i have a lack of trust in her no real reason why and sometimes i just feel like i just flat out don't like  her mainly when fighting. she also has a lack of trust in me for no reason as well. when she was living with me everything was great because we would always know what was going on with each other and have that comfort knowing we were coming home to each other but when she moved back to her parents we broke up for two months i filled the void and soon after she did too we then started talking again and talking about what we needed to work on but it always gets turned on me its all "my fault" things go wrong no matter how much i take her out buy her random presents tell her how much i love and care for her we always end up fighting again and it always gets blamed on me what should i do i don't know what to do anymore i love her and want to be with her but i want to be happy more than not. please give advice need help