What Causes Irregular Periods Along With Severe Abdominal Cramps?

Hi I have a bad history of losses during pregnancy which nearly all but one have to be removed by D&C, one was a triplody baby and another was a hydatidiform pregnancy which I had to have follow up for nearly 3 years, I also have 3 children 2 of which were emergency sections and one of those I ruptured during labour with which was 5 year ago. For the last 9 month I have had irregular bleeding which has worked out I bleeding about 4 times a month, and im also suffering quite badly with cramps and back ache. I went for an ultrasound and they have found my uterus lining is 11mm thick but my consultant wants to wait to see if this settles down by itself before making any decisions to investigate. Should I go for a second opinion as im quite worried considering my history. Im 34years of age and have been pregnant 9 times in total. Thank you any advice is very much appreciated