What Is The Reason Of White Discharge And Spotting In Between Periods?

I am 34 years married and have three children(all delivered normal).since last two months I had experienced spotting between my periods.it lasted only for a day or two.in the first month it was thin red blood but in the second month it was dark clot.my cycle used to be normal of 28 days.last month I had experienced heavy bleeding too which lasted for 5 days.my last period was on 22nd of December.but this month I haven't got my periods yet.i know I m not pregnant as my husband is staying abroad.i m also having a lot of white and watery discharge.i never had such kind of problem before.could you plz tell me what might be the reason.thank you.