What Causes Body Rashes, Fatigue And Joint Pain After Child Birth?

To start off I m a female, 23 years old. Two years ago I had my first son, before his birth I was very healthy. After his birth I developed weird symptoms, skin rashes, dizziness, weakness, joint pain, headaches, low grade fevers, floaters in eyes, dry mouth and eyes, light sensitivity especially in eyes, stomach problems etc. It started with the skin rashes and I went to a derm, they said it could be scabies and gave me multiple rounds of the treatment for that(feel like the cream could have triggered an immune response), still was getting rashes and was on prednisone for awhile. The rashes would come and go. I had my second son 1 month ago and during the pregnancy the joint pain, bad headaches and neck pain, swelling and rashes continued. Had a few incidents of numbness in my hands and feet during the pregnancy. Developed bad sinus problems too. Was getting sinus infections every other month. My OB pretty much blew me off the whole time and said it s pregnancy and go deal with it. The joint and muscle pain was so bad I could barely walk in the mornings and my headaches and brain fog continued to worsen. Since November I ve also come down with 3 bad colds and feel like my immune system is non existent. Even when I m not sick I have chronic sinus problems. Today I just got back from the dr and have a swollen pus filled tonsil, fever, and swollen neck glands. What could be wrong with me? Could my first pregnancy have triggered an autoimmune disease? Could the rashes be Lyme? Or could this be something completely different? Plan on seeing a regular dr this week and getting blood work or a referral. All of these problems have caused me to have bad anxiety as I have no clue what s wrong with me. My OB put me on Zoloft because I think he got tired of hearing me complain :(