I haven't had my period since I gave birth to my third child. He is 4 years old now. My estrogen is <25 and now I am wearing a the Vivelle Dot to give me the estrogen I need. I am only 32 years old. Is this safe for me to do long term?

Complete blood work was done at my yearly exams 2 years in a row. Both showed that my estrogen was <25, FSH and LH were very low as well. Everything else came back normal. My doctor just prescribed the estrogen patch in the spring to help prevent osteoporosis and to help with some of the symptoms of low estrogen. I have had no previous history of amenorrhea but my younger sister hasn't had a period for years. I breastfeed for a full year with all my three kids. I never had a hard time conceiving my three kids. I became pregnant with them within a couple months of trying. I have been through several rounds of fertility treatment to try and have a 4th. I was unable to ovulate on oral medications and did 3 months of gonadatropin injections. I ovulated two of the months and hyperstimulated one month. I never became pregnant. We have decided to stop with the fertility treatments. I am a small women and asked my doctor if she thought it was my weight and she said she didn't think so. I just want to make sure that the estrogen patch is safe to use at such a young age. I wonder if it is safe to use long term if my estrogen still continues to be low. I don't want to get cancer.