Hey everyone

I have recently rescued 2 labs from high-kill shelters in Indianna. I LOVE them dearly, they are so much fun. My 2 yr old yellow lab (not neutered yet) has been displaying some anxious behavior lately. He barks and runs around and cant settle in. Yesterday I took him to the pet store where he barked at all the dogs and got so worked up he went to the bathroom all over the store. I am not sure if its because he is not neutered or is there something else making him so nervous. Can anyone give me some advice?
Thank you much, look forward to hearing your thoughts!