After sex issues

Okay hi!! So about 2 days ago I had unprotected sex but he pulled out I had it twice and both times he did but I didn't pee before or after till later on and it's since when I pee blood comes out and hurtssss! Sometimes there's nothing and it's fine sometimes it's a lot or a little this happened before when i lost my virginity but not since , I took antibiotics before and that helped and all was good should I just do that again ? I wanted to know the cause of it and how to prevent it cause it's not fun !