if a receiver is forced out of bounds,is he eligible for a reception?

Players eligible at the start of the down remain eligible throughout the down. rule 7-5-6d.

What I think you are looking for is whether he commits illegal participation. Rule 9-6-1.

If any player is blocked out of bounds by an opponent and returns inbound during the down, he shall return at first opportunity.

So if he is forced out and returns inobunds as soon as possible, it is not illegal participation.