Hubby, No Chubby

That's an awful title 😂
Anyways, my husband has been having trouble staying hard when turned on. We're in our early 20s. I thought this was an elders issue? If we don't have sex for a couple days he's fine, but if we have it more than that he can't stay hard long enough to finish. 
Is this erectile dysfunction? Can this cause issues with TTC? 
Don't worry, I make him feel like it's no big deal but it's happening more often. (TMI) Seemingly for a few days after he cums a bigger amount.Â