Hello Dazue, try doing these steps and see if this helps. If what Barefoot Tiger has said did not help, and these steps don't rectify the problem either, I'm afraid your save is corrupt.
1. Save in a new slot, then reload the game so it loads the new save slot.
2. Kill your character.
3. If nothing is still on the map, proceed to Online, play for five minutes and exit back to SP through the character switch wheel. (If you don't have online, then just skip this step)
4. Next try going to your safehouse and sleep on the bed, but hit B or Circle so it doesn't save.
5. If nothing still, kill your character one more time.
If all fails, then you'll be forced to make a new save. To prevent something like this from happening again, every 5-10% progress you make, save in a new slot. Cycle through 3 save slots and always save in the bottom slot so the oldest save is moved to the top. That way, if the game becomes glitched again, you don't have to backtrack very far. Let me know if any of the above steps helped or not, and good luck.