I'm about 5'7 feet tall and age 18. is it possible for me to grow a few more inches?

Unlikely: I wish i had better news for you but you growing days are pretty much over.

Depends: It can be possible. People, don't turn off growing at precisely 18. Genes play a big part of your height. It would depend on if your growth plates are completely closed yet or possibly still open. I'm a fan of college basketball - some of these guys are still growing as freshman. 5'7" is not a bad height even if your growing is all over.