Hector,
To add on to MrPogi, are you getting any VHF channels, including VHF-Hi (7-13) or VHF-Lo (2-6)? In your case, these would be 33-1 (RF 5), 9-1, 6-1, 11-1, 13-1, and the more-distant 12-1 and 8-1.
If you're not receiving these VHF-band channels, it's likely your antenna isn't picking up VHF. If you are, then something is interfering with your signal, and there's any number of things that could be causing it.