Should I call my doctor????

I'm between 4 and 6 weeks pregnant. All day today I've felt a lil off first thing this morning my belly/lower belly felt kinda bloat like I had to poop but I didn't. Then for about the last 8 hrs my belly has felt tight, it kinda comes and goes I mostly notice it whenever I go to stand up or pick anything up. It scares me that I may be gettin ready to miscarry, is this possible? wat should I do? Should I call my doctor? Has anyone had this before this early in their pregnancy... Please comment with your opinion