My starter stays engaged until I put my car in gear what could be making this happen someone told me it could be my ignition switch

It could be the ignition switch, as has been suggested to you. Try this: as soon as the engine starts, rotate the ignition switch slightly back (counterclockwise), but not enough to shut the engine off. If the starter stops when you do that, your ignition switch has a weak or broken spring inside, and needs to be replaced.

How often does this happen? rather than reply first , throw an ignition switch at it , then when that doesn't work , let us know..........................................................