Hallow Mumma, The main question is whether you had started your menses after the delivery, or you are still without menses (locational amenorrhoea). It is possible that in this period, particularly when your baby is 7 months young, the eggs may start getting released even though you do not have menses. Then the risk of pregnancy arises. However, if you have already started menstruating, missing a period will be the first symptom of pregnancy. As you have rightly suspected, breastfeeding could be a cause for the soreness in the nipples. The back pain shooting to your buttocks is most likely to be due to position and calcium deficiency which is very commonly seen in mothers breastfeeding their babies without taking calcium supplementation. Please start drinking at least 500 ml of milk daily in divided servings and supplement it by calcium tablets. If you can tell me about your menstrual history by asking me Direct question, I can further opine on the possibility of pregnancy. However, since your baby is now 7 months young, it is advisable that you start on to some reliable birth control method like birth control pills, condom or intrauterine device. Hope this helps you. Dr. Nishikant Shrotri