I dont know if he likes me or not?

so i became really good friends w/ this boy.. lets call him zack (not real name). the problem is zack has a serious gf. even though we’re in jh. well i really really like zack and he acts like he likes me back.. hes always teasing me and poking me and making me laugh.. that sort of stuff. but ive never been good at this kind of stuff seeing as how ive never really had a bf before. but i just really need help because idk what to do!! thanks :)