Emergency c-section two months ago constipated and no periods. is it safe to start having sex?

Probably: You should have had your 6 week check up where your OB usually releases you to sexual activity. If you haven't had that visit, I would do that first to make sure you are really released. But in general 6 weeks is usually a reasonable time to resume sexual activity. Use birth control and/or a condom unless you want to become pregnant again soon.