Would I Have An STD from this ?

I'm 12 and there was this guy a little older than I was and he was my first boyfriend like I had never kissed anyone or anything. But one day we were hanging in my room. And he did some stuff ( if you know what I mean ) and he only had his thing in my for a small bit of time then I told him to leave. But that isn't the problem. 3 months later I dated this other guy who knew that bf, he told me that that kid had STDS since 5th grade... And he told me I have them. But I don't feel any different and I know I don't have herpes. But I have a drunk abusive mom so I'm not really gonna go ask her if she can take me to the doctors cause I might have an STD ... Id probably get thrown out a window if she even found out I had a bf. But still is there ANY way I can find out If I have one , it's been 6 months since he did that. I am very paranoid. I won't even go swimming because I'm so embarresed ... Somebody help. I really have nobody to talk to about this..