Why do guys start being weird after you have sex

He knew that I had a boyfriend, I made that clear, and he said that he wasn't sure how he felt about that, but afterwards said he still liked me and wanted to have sex, however I considerEd that he might think I was developing feelings for him, and thought that was silly because I'm already with someone else and it was and ways going to be no strings attached, he has since confirmed that he wants to do it again, but we just don't talk, so I'm just gonna leave him to it

So recently me and my bf decided we wanted to experiment in our relationship, so we opted for doing the whole "open relationship" thing, but bearing in mind we were both each others first when it came to sex and getting into a proper relationship, and we had never done anything like this before. So anyway we set up Tinder accounts and I started talking to a few guys, one being a guy 7 years older than me, and since the age difference was fairly big I didn't think anything of it, except that we proceeded to talk for like 5 weeks and then after meeting up for the first time (nothing happened) we decided to meet up again like 2 weeks later, obviously for sex. My bf had something set up on the same day ironically but he was going to be staying out. I wasn't bothered by this. So me and this guy are chilling at his and we **** like 3 times (after the first time I was told he would definitely want to do it again) and at some point we ordered food, he paid and said that I could pay next time (again insinuating that he would want to do it again) so then we cuddled cause apparently he's a cuddley kind of guy, and we did this for like 30-45 minutes. then the next day I didn't message him because I wanted to suss out the situation: would it be the typical guy ignores girl, or would we just carry on being normal, so I left it up to him to see what he would do, after a while he messaged me like normal, so I thought I had my answer. So I messaged him the day after that and he saw the message and just didn't reply? I didn't message him again that day, but did again the day after that just to see if he was okay, and he seemed fine, he replied, but when I sent him a picture of something I thought he'd find funny he saw it and just didn't say anything again, this happened a few more times. But the point being is that I don't understand this kind of behaviour and its really confusing me? I don't know whether to just not bother messaging him again and leaving him to it, or being direct and asking what the deal is? Because the problem is that he seems like a cool person so I'd at least like to be friends, and I'd also prefer to remember him as that cool person instead of a someone who turned into a dick afterwards? So what's his deal and what should I do

I was expecting it to be ab bout your bf.

Men arent all the same. You barely know this one. Tinder is commonly just used for sex. His idea of what happens after differs from your. You think casual be be reasonable contact with each other, he thinks sex and interaction when it suits him plus he doesnt wnat anything clingy( even if you arent) plus he might be sleeping with others. he could just be busy.

Imo treat him like a fb ( dont think he could handle a relationship) pr just move on.

That makes sense, I've considered all these things, he said it had been awhile since he'd last had any sexual interactions, and when he does talk to me he complains that he's bored, but I've gone for moving on lool