Hello,
Hopefuly I got the calculations right 
-> this is my first time, I hope they will help you.
1. Probability that someone flopped the flush, and you're not holding the best hand now.
(<Probability of beeing delt 2 suited cards> / <4 possible suits>) * <no. of players>
(23.5% / 4) * 5 ~= 30%.
Take a note about a multiway pot, for each player in the pot you should consider 6% (23.5% / 4) that someone flopped a flush.
Even in this situation you still have 7 outs + some outs for the same card on turn & river, which according to poker calculator, give you 35% chance of winning in this situation.
2. You're holding the best hand -> let's see how many times you win. I assume, that if another heart comes you loose.
I calculated this using hand calculator (KK against nut flush draw with this flop), and you win 70% of the time & lose 30%.
3. Adding this two situations.
Win Rate: <prob. of someone flopping a flush> * <your chance of improving> + <prob of someone flopping a flush draw> * <your chance of staying ahead> = 30% * 35% + 70% * 70% = 10.5% + 49% = 59.5%.
4. There is also straight draw possibility, but this is rather marginal, so I'll skip the calculations and will say, that you'll loose to a str8 only ~3% of the time.
Summary:
As you can see, you'll win here more often than you lose and you should push as much on the flop as possible, so you played it correctly. If a heart would come on the turn, you should call the raises according to the outs & odds to see if you've hit a full house.
This calculations were made assuming a Heads-Up situation after the flop, but since there is more than one player after the flop, your EV rises even more.
Hopefully these calculations are right and helpful. If I made some mistake, please point it out so we could all benefit :).
GL at the tables!
