is my boyfriend lying?

so my boyfriend and i have been together since september 2018, though we went on and off at the beginning of 2019 due to a lot of things happening. we both were each others first time, but he did a lot of hurtful things and disrespected my boundaries a lot and it caused me to have extremely bad trust issues so i ended up breaking up with him again which has been the last time we had split, and that breakup lasted a month until we got back together. how we got back together was that he was stalking me on social media and so was i but him knowing that he posted a bunch of sub-tweet kind of things about him being depressed and talking about things that would be trying to get my attention pretty much and i messaged him to stop but then just started venting and we were talking again i guess. he said he wanted to tell me something important in person, so he wanted to come to my place in person to tell me. when he did he told me he had sex with another girl, he didn’t say her name or who she was but decided to tell me he took her virginity. he told me he kicked her out right after and immediately regretted it. soon after like maybe weeks later he said he didn’t kick her out instead he said to her that she should leave which seemed sketchy he was switching the story. months later after there were more things he was doing like disrespecting my boundaries and being hurtful(not physically or abuse related, jus doing rude things and not really caring about me or prioritizing me at all) i had enough and told him what he’s been doing and how it’s effected me etc and i told him he needed to tell me who she was and tell me the truth. he told me her name and that he found her on tinder, that she was 17 (he’s 18) and that they talked for a week and that she drove across the state to have sex with him, and then an hour after he told her to leave late at night. the next day they were still texting and he said he told her he didn’t feel right with what he did and then she blocked him and that was it. i asked for her instagram because i didn’t believe what he was telling me and she sounded made up being 17 and driving across the state and being on tinder, but he “didn’t remember her username” my friend says this story is sketchy and i always see things about “trust your gut feeling” and i can’t tell if it’s that and if i should because of the amount of anxiety i have and trust issues. i would like to hear others opinions if he is lying or not about this. i really wish i just knew because i throw up and cry and have so many panic attacks thinking about this, it just hurts me, i know we weren’t together but not even a month after breaking up this happens? and the way his story changed a bit a few times? and the way he left important things out but chose to tell me she’s a virgin? him “not remembering” her username on instagram, but had remembered usernames he followed again when we split that i didn’t like (instagram models etc to make me jealous when we broke up)? idk i really need to know if i’m just overthinking. i’m reposting this to get more opinions if he is lying about this or not.