@Nikkoi "Well idk how it will benefit you since in your level, you probably wont get that position again in a long time."
True, but we can discuss general principles here, which should come in handy in any game.
@YouGetNoRest "I don't think analyzing blitz is very useful to your overall growth as a chess player."
Agreed, but we are not analyzing a blitz game, but a single position which could easily have appeared in a long time control game, as it is quite typical.
My two cents: As already mentioned, White's threats are 1) Nf5 halving your bishop pair and 2) c4/e4 breaking open the position resulting in an awkward situation for you (after all, d5 is attacked 4 times). To meet both positional threats, Qe5 suggests itself. I'm 100% certain that this the best move for Black in the position, without checking the engine evaluation. It nicely centralises the Q on a square where it cannot be attacked easily. Nimzowitsch was right: When in doubt, centralise!
Now for the long-term plan. You are completely right, you have the bishop pair and this can become an eternal positional advantage if you manage to open the position in your favour. Therefore I would think about the move order 15....Qe5 c3 (looks logical, gives the white B new life) and then f5, intending an immediate f4. This would force open the f-file, which improves the potential for both of your rooks, and they work together nicely with a B from c5 attacking f2.
If White meets this with Ne2, I would seriously consider g5, gaining more space on the K-side and preparing f4 and g4 pawn pushes. White's pieces are not aimed at your king, so he cannot exploit this weakening for now. Note also that your center is currently stable, so pawn breaks are not yet possible.
This might all be nonsense, since I didn't check with the engine, but at least that's how I would approach the position.