He has physically slapt me verbally abused me

I have been with my on again off again boyfriend for the last 3 years he has physically slapt me verbally abused me calling me b*h whore slut cunt moron the list goes on also he constantly blames me for everything even when hes wrong. I also feel he might be either gay or bi he has asked me numerous times to lick and play with his well the anal area hes also asked me to have sex with men film it and give him the video he says it turns him on also for his birthday this past year he spent it with a buddy of his drinking beer watching a movie in his room with the lights off. This has all taken me by surprise due to the fact we have been close friends for over 13years and grew up togther he had been after me for almost 5 years and after I got divorced is when we had gotten together. I beleive I have done more than most girlfirends would do for him such as support him for almost 2 1/2 years shower him with gifts clothes vacations even having a 3sum with his ex girsfriend the list goes on. He’s also cheated on me multipule times and one of the times his best buddies told me of one of the times. I dont know what I’m doing or have done so wrong other than love him deeply and have tried to make him happy for him to treat me this way. Yes I have not been perfect either but we all make mistakes and he knows of them as well. It just seems like if I dont do things his way I’m wrong and one minute he will lash out at me and after he calms down he calls and acts like if nothing ever happened I just feel like hes constantly playing mind games with me and is confused about his sexualty and thats why he treats me so badly. Could this be a logical explanation for his actions or am I wrong? Please be very honest with your answers. Thank you