First, welcome!!! So glad you decided to post, you can respond to our topics any time

I would say that it might be a combination of things - it could be a side effect of his shots, it could also be a growth spurt where they sometimes go through sleep regression. I wouldn't be too concerned because unfortunately babies sleep habits change all the time, just when I think my son has a schedule he changes it again! Hang in there I'm sure it will be back to normal soon!