I am so sorry to hear you're going through this. I can't give you medical advice. But I will say that my last surgeon, who operated on me this past March, told me that if my pain continued or came back 3 months after my surgery — that's how long he told me to give myself to heal — then a second surgery within a year wouldn't be a good idea. He says that's because surgery itself causes scar tissue and other problems that can lead to pain, and if it didn't help the first time, he didn't feel confident it'd help so soon after.
With that said, I would definitely bring up your concerns with a medical professional. You can see a different doctor to get a second opinion. I'll admit that I'm not familiar with letrozole as a treatment for period pain and/or endo. But every doctor seems to treat each patient differently. That's one of the unfortunate things about endo — there is no real consensus on the best way to treat it when pain continues after surgery.
I'll also say that my surgeries (I've had 3) have helped ease pain with sex and exercise, but they've never helped my period pain, which is severe. My endo specialist thinks that's because I likely have adenomyosis -- it runs in my family, along with endo. And right now, the only way to treat that is with a hysterectomy, which I'm not willing to do. Has your doctor ever talked about adeno with you? If you have very serious bleeding with your period, there are medications that can lessen the bleeding and clothing. That sometimes helps with pain. Though, that's not something I've tried. Currently, I'm on a preventive pain regimen that involves ibuprofen, which is anti-inflammatory and helps slow down blood clotting . My GP has suggested I take it for the 5 days leading up to my period. So far, it has really lessened the intensity of my pain. My periods are also easier to manage.
I'm hoping you find answers soon. Whether you decide on another surgery or not, ask your doctor to come up with a pain management plan. That's what I did with my doctor even though my last surgery did help with other issues. If your doc doesn't give you a plan that works, ask to see a pain management specialist. They have all kinds of tools to help. Keep us updated on how everything is going. In the meantime, wishing you well! - Keri (endometriosis.net team member)