Hi, I had gone through your question and understand your concerns. A painless bump on labia may be a considerable problem,because usually small painful blisters like or small pimple like things are common due to closure of sweat glands or sebaceous glands ducts,this is very common during pregnancy due to hormonal changes. Pain less bump is also common in SYPHILIS which is a SEXUALLY TRANSMITTED DISEASE ,this could be a problem ,and may effect the health of the baby. It is better to rule out this by VDRL test.This will rule out all 5 infections (TORCH). If it is positive you should get a complete treatment for this. Consult a gynic and get an examination as soon as possible. If you have similar problem before ,give a notice to your doctor. If the VDRL is negative you can just leave and use some moisturizer. Your back-pain ad muscle pain is due enlarged uterus pressing over leg ligaments,is a very common problem.Take calcium and iron tablets regularly,take more water.Get high fiber diet to prevent constipation. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions.