My 4 Yr Old Cockapoo Has Been Having Accidents All Over The House. Any Suggestions?

I feel like my cockapoo was never 100% house broken. He has always had accidents here and there. But lately it has been terrible. He has at least 2 accidents a day, both #1 and #2!!! We just had our first baby 6 months ago so I don’t know if he could be jealous and doing this out of spite. Any suggestions for re-training him? Is it even possible since he is already 4 yrs old? Help!