Nice Bet on the flop but he followed you. That mean usually he have something or running after it. You had two spades on the flop, that should ring bells.

When the third spade appears on the turn, you should make your decision, put him on the flush and fold or betting for information. your 2$ bet on the turn don't give you any information, you gave him a 4to1 pot odd wich its usually good pot odds. If you really wanted to know if he have the flush, you should bet 3/4 the pot or the pot. In this case, the results would be the same, meaning losing 4$ or a bit more, but in a long run, you have to get the information