Is my boyfriend bi

i m a femal. recently this gay boy a total catcher that i work with told me that my boyfriend left him a ten dollar tip, and when i use to be the server the most he gave me was five. but any way i said yeah he always tip, but he give the women there no more than three dollars. well my boyfriend tell me everything especialy if he go to my job and eat, he never mentioned the tip but he did say he went there to eat. a week in adavnce my boyfriend asked me if the new boy who works at my job was gay i told him yeah isnt it claer. i didnt think nothing of it. we had sex the following day after the ten dollar tip and he was fingering me while fingering me he was also placing a finger in my anus i didnt feel it at first until he started putting it futher in. the entire time he was fingering me i was jagging him off he became turned on and started placing it futher in my ass it started to hurt i tried to pull away but he kept sticking it in and his penis was becoming more eract. i was confused because i did not think he was trying to pleasure me it seem like he was worried about his own disire. i tried to climb on him since his dick was hard but he kept his finger in my butt and gave me the signal to rubb his dick. he didnt even want my pussy, then he seen that i was not having as much pleasure as he was he then allowed me to climb on his penis. although that was weired the sex was still pleasurable i dont know if i was making it out to be more than it was because of the gay guy from work or do my boyfriend has the desire for a man's ass. we have been dating nine months and this is the first time he ever put his finger in my butt and was turned on. please help me is my boyfriend bi or does he just want to spice up are sex life.