pop ups every time I change open a window

This issue started a few weeks ago. Frequently, when I switch from one page to another, I get a pop-up page from some unrelated business or form. I have started to fill out an order form for a trusted business only to find out I am filling out another company's form instead. My page gets hijacked in this manner several times a day. It's not only annoying, but a security issue. One moving company keeps popping up. I am not moving, or even thinking about moving, but I keep getting this company's home page when trying to access other venues. I don't know if this is related, but I installed Duck Duck Go a while back to avoid Google trackers. A few weeks ago I found that Duck Duck was no longer my preferred search engine and put it back as preferred. Whether coincidence or not, my problems began about that time. Please help. Regards, Bill Okopski