My boyfriend bought me a truck as a gift we are breaking up after 15 yrs and now wants to take truck away from me is there anyway j can fight to keep

With minor exceptions, gifts are not revocable.  One exception which may be relevant here (and on which the laws of the different states vary) is a gift in contemplation of marriage, usually engagement rings.  No other exception seems applicable from what you've written, so assuming that this exception does not apply here, your boyfriend can't take back a gift he has given you.  HOWEVER, your ex may claim that he did not give you the truck, but only let you use it while you were together, or some similar explanation.  Without knowing any other evidence (e.g. in whose name the truck is titled, who made any payments on the truck, who paid to maintain it, is there anything in writing or any other uninvolved witness who can prove the gift, etc.), I can't guarantee that a court would not believe him.