My bottom teeth are crooked again from not wearing my retainer if I get a new one and wear it with my original top one that still fits would it be ok?

Orthodontist. Have your orthodontist evaluate your relapse. It may just be a minor fee to align those lower teeth, then you can have new retainers made. This time around, wear as directed.
How unfortunate. Retainers retain, they don't correct. If bottom front are crowding it means back teeth drifting forward. See your Orthodontic Specialist to determine appropriate course of remedial treatment.
See orthodontist. so they can evaluate the teeth and recommend the best course of action.
Retainer. A retainer will retain or keep teeth where they are. If that suits you then your plan would certainly suffice. You could elect orthodontic treatment of your lovers again. This would be an opportunity to straighten bott teeth. Then retain them there. You are young and orthodontic treatment would serve you for a long time. Besides aesthetics or good looks straight teeth are easier to maintain .