Am i stupid for putting up with an asshole? -_- HELPPP?

So i broke up with this guy a week after we went out because of my parents. We decided to be just friends after and it was cool at first, but now he's been acting kinda mean towards me. He'd embarrass me infront of his friends, say things like "why are you talking? what are you laughin' at? why are you sitting next to me?" in a joking, yet serious tone. Also, his friend would look at me and shake his head and say "im disappointed in you kid" but he wouldnt tell me why. i guess they were joking but his older brother (lets call him Dennis) likes me as a FRIEND (he's like a big brother to me nothing more) and he invited me to hang out with him and come to his house last week. i accepted, only thing is that his brother was also gonna be there and so the mocking began. his friend's girlfriend pointed out how he was being a real dick to me. He then asked me "Am i mean?" and i said "well yeah" and he said "fine then i just won't talk to you anymore" but in a joking kinda tone then everytime i said something to him he'd say "oh wait im not talking to you remember?!" so it was weird but i still like him and Dennis (his brother) said he was gonna invite me over his house this summer so we can watch soccor games. All his friends (including his brother) like me and think im cool and treat me nicely but my ex is acting like a jerk to me, but when we text he always ends up talking about his problems. me being me of course, I start to forget about all things hes done to me and i comfort him and give him advice. so can anyone tell me what the heck is going on? what i should do? should i go over his house even though his brother and friends are the one inviting me?