If i got a tdap 4 years ago could i get one done again now?

Yes, But: It is generally recommended to have the TDAP every 10 years unless you have a major accident or cut that might introduce the tetanus bacteria into the system quickly overwhelming the protection you have. TDAP is good at preventing re-infection from routine scratches, scrapes, mild cuts not needing stitches etc. when taken every 10 years.

I wouldn't: If you completed the primary vaccine series in childhood and had a booster 4 years ago another now not accomplish much. There are some medical conditions where your doc might consider it, but I would consider it a waste of time and effort.