Regretting his decision

So I don't have any children and never wanted any. I've always been on birth control but a little over a year ago I got off of it because I was just so over the hormones, I was always so irritable, depressed etc. Anyway my SO was cool with me getting off bc because he obviously saw how it affected me but neither one of us wanted kids/anymore kids. He has 2 children from a previous relationship. They're older now (17 and 22) so he definitely didn't want to start parenthood all over again and again I have never been one to want children so I was content. Well since I was off birth control we started discussing permanent methods like tubals/vasectomies. We did the research and it appeared that vasectomies were much easier and less painful than tubals so he took one for the team and got a vasectomy. He got it done on 1/10 so it hasn't even been a week yet and I find myself thinking about the what ifs of never having my own children. I WANTED this but now all I feel is regret. I'm hoping this is a normal feeling and I'll get over it. I'm 30 years old and my SO is 40. Anyone else experience this and how did you handle it?