Ok I recently put new headlight bulbs in my 2001 f150 but now only one headlight works in the low position. But both high beams work any help. Could it be fuses?.

 

In my 2003 manual, there are separate fuses for right and left low beams. If your setup is the same, they are fuse 26 and 28 in the inside fuse box. If you don't have an owners manual you can download it:

http://www.fleet.ford.com/maintenance/owner-manuals/

If the fuses are good, you sure the bulb didn't blow? Swap sides or try one of the old ones if it still worked when you pulled it.