and now the gate to The Strip is locked and says i must have a key to enter is there any way around this or am i screwed

You have 2 options, that I'm aware of, anyway.

• If you have an item of NCR clothing, or high-ish rep with the NCR, you can use the monorail in Camp McCarran
  
• You can kill a robot at the gate and loot the key. This option is by far the most dangerous, however.