A lucky win

As black in the following encounter against someone rated much lower than me, the game progressed slowly, with lots of manoeuvring from both sides.
1. d4 Nf6 2. Nf3 d5 3. Bg5 e6 4. Nbd2 c5 5. e3 Nc6 6. c3 h6 7. Bh4 Be7 8. Bd3 O-O 9. h3 c4 10. Bc2 b5 11. a3 a5 12. Bg3 Bb7 13. O-O Qb6 14. e4 dxe4 15. Nxe4 Rfd8 16. Qe2 Nd5 17. Rfd1 Rac8 18. Ne5 Nb8 19. Qh5
White could have pushed for some queenside play with 19. a4 Nc6 20. axb5 Nxe5 21. dxe5 Qxb5 22. Nd6 Bxd6 23. exd6
19…Rf8 20. Nf3
(20. a4 b4 21. Rac1)
20… Nd7 21. Ne5 N7f6 22. Nxf6+ Nxf6 23. Qh4 Qd8 24. Qf4 Qd5 25. Nf3 Nh5 26. Qe5 Nxg3 27. Qxg3 Qh5
(27… Bd6 28. Qh4 f5 29. Re1 Rf6)
28. Ne5 Qe2 29. Rac1 Bg5 30. Re1 Qh5!?
We could end up in a perpetual after 30… Qd2 31. Red1 Qxc1 32. Rxc1 Bxc1 33. Nd7 Rfd8 34. Nf6+ Kf8 35. Nh7+ Kg8 (35… Ke7 36. Qxg7) 36. Nf6+ whereas I was interested in keeping some tension in the position. I was rewarded almost instantly with a blunder by my opponent.
31. Rcd1 Rfd8 32. Be4??
Forgetting that the trade of bishops would leave his rook hanging on d1!
32…Bxe4 33. Ng4 Qg6 34. Ne5 Qf5 35. Ng4 Bd3 36. h4 Bf4 37. Qf3 Bd6 38. Qh3 h5 0-1