Why Do I Feel Pressure In Abdomen While Removing My Tampons?

I have noticed the last few periods that I have a lot of pressure type pain when removing my tampons, no matter how full they are. I am also noticing that when I urinate during my period, I experience a lot of painful pressure in my lower abdomen, even without a tampon in at all. Any idea what may be causing this? I am 37 years old and have used tampons since I was 15. I have 3 children and this only started a few months ago.