Period Problem. Me what's wrong with me.

Hello Doctor, I am 26 years old. Since March I have been suffering from periods problem. Before March my period was regular. The cycle was of 28 days and it lasted till 6days. But I got my period on 7th march which was 22nd day of my cycle. The flow was normal but it lasted for 7days. Then i got period again on 23rd March. This time it also lasted for 7days. Then I got period on 4th April after that and again got my period on 26th April. Every time it lasted for 7days.sometimes flow was heavy sometimes the flow was normal. Each time my period accompanied with nausea. During periods i didn't feel much pain. But after my period completes every morning i feel nauseate and also excessive burping in empty stomach. I don't feel like eating anything because I don't feel hungry anymore. I am not pregnant but i have a history of PCOS. I didn't take any medicine for that for last 1 year. I gained 10kgs in last 2 years. I also have Rheumatoid arthritis. kindly tell me what's wrong with me..