What's an "okay" amount of times to have sex per week, for a married couple?

In the late 20's, both working full time, parents of a 7yo, opposite work schedules. I'm just trying to find a balance in this here marriage 😩, we want another child desperately but I can't seem to find the energy to put the work in to satisfy my husband. It's putting a strain on my marriage I believe 😪