I'm really getting scared

Hi, I'm new here. I came across this forum and I hoped someone could help me.
I'm having a really bad time with constipation. I've always had problems but nothing this severe.
Here's the story
Haven't been able to have a bowel movement in three weeks. doc said try ducolax stool softener, I did that for seven days and nothing. Next, he said Miralax powder. I did the miralax every evening followed by two bottles of water, I did this routine for eight evenings. I called him and he said a suppository will work. Did that this evening. Directions said try to hold it for fifteen minutes. It's now been two hours and nothing.
I have no appetite at all, I'm drinking plenty of fluid.
I am also a Breast Cancer survivor of five years. Last year I had a near fatal heart attack.
So tired of these health problems. I'm afraid the cancer may have returned but I've recently had plenty of bloodwork done and it's good. Also afraid of maybe having an obstruction. Any suggestions would be so helpful.
thanks and sorry this is so long.