Left the b2 pawn unprotected in a sicilian

I was playing white against sicilian.

1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 d6 6. Be2 g6 7. O-O Bg7 8. Nxc6 bxc6 9. f4 Qc7 10. f5 O-O 11. fxg6 hxg6 12. Bf4 Qb6+ 13. Kh1 Qxb2 14. Qd2 Nh5 15. Rfb1 Qxc3 16. Qxc3 Bxc3 17. Bd2 Bxd2 18. Rd1 Bc3 19. Rab1 Nf4 20. Bc4 Be6 21. Bxe6 Nxe6 22. Rb3 Be5 23. h3 Nc5 24. Rbb1 Rab8 25. Rxb8 Rxb8 26. g4 Nxe4 27. Kg2 Rb2 28. Re1 Rxc2+ 29. Kf3 Ng5+ 30. Ke3 Nxh3 31. Kd3 Rc3+ 32. Ke4 Ng5# {White checkmated} 0-1

12 Bf4 was the place I commited the mistake. My opponent made me pay for it.
I could have got away with just a pawn had I done 13 Bd2 instead of 13 Qd2
15 Rfb1 was another mistake. I could have gone for 15 e5