You are still young enough to have another child. If you are in optimal health and think you might want another, then maybe you should consider another means of birth control until you are sure. This sounds like a good time to step back and re-evaluate one more time before making that V cut.
My husband and I have four children - the last is 12 years younger than our former youngest. I was in my 40s at the time, so the stress levels and issues would certainly be different than what yours might be. If your children haven't adversely affected your relationship with your husband so far, then it is doubtful that another child would change that relationship, especially with your youngest still an infant.