Adding to the above: Biological children with your spouse is not the only option. Adoption or fostering are two other. But again, it sounds like this is project

Adding to the above: Biological children with your spouse is not the only option. Adoption or fostering are two other. But again, it sounds like this is projection more than anything else and your mental issues are not actually caused by you not having had children. It sounds very likely that even if you magically had a baby with your SO tomorrow, this would not be the "solution" you are looking for. Maybe it wouldn't be long until you feel the same level of regret over having had a kid, only now with an additional level of guilt. Raising a child should be about the child first and foremost, not about you trying to resolve your existential crisis.