Once you've bet turn you must fold to raise there.

I would recommnend you get into the habit of making all your raises 3x your opponents bet. If your top pair is good and he has a flush draw you are giving him over 3-1 immediate odds with this min raise. By raising 3x you will perhaps push someone here off a hand like JT/JQ. Also if you flop a set and someone has TPTK/overpair you start to build a pot and commit them to it.