I've taken amoxicillin before, can i become allergic to it?

Yes: It is possible to develop an allergy to a medication even if you have taken it before. There is nothing you can do to prevent this though.

Yes: you can have an allergic reaction to a medicine you have used in the past. In fact, that is the usual course of events.

Amoxicillin: As you have taken before, so you are not allergic to it. Rarely, you can become allergic later in life.

Yes: An allergic reaction can still develop even after many prior exposure.

Not necessarily: taking a medicine frequently is not a reason to become allergic to it, allergy can develop to a certain medicine after taking it for years, for different reasons most of which are unknown, if you suspect you have an allergy to any medication, go to any hospital ER waiting room, take the medicine, wait for an hour, if nothing happens leave, if anything happens though , you are in the right place

Yes. Get tested.: Yes, in fact, classic allergy requires previous exposure in order for allergy to happen. There exist reliable data on skin testing for allergy to penicillin-type drugs. Plus, after about a decade where the most important penicillin skin testing ingredient was unavailable, leading allergists managed to bring it back, and once again it is available to allergists for testing. Call and get tested.