Pregnancy question for a beginner?

I'm approx 5 weeks pregnant. I had a confirmed blood test last Wednesday and got the YES I'M PREGNANT answer, which I stoked about, but the thing is since I found I have been pregnant I have had a dull ache in my lower back and minor aches in my pelvis area. They are tolerable, but some days the back pain is just full on, where I can barely stand OR walk.I'm terrified something is wrong, at the present there is no blood, but the pains only get worse sometimes in my back. Is this common in pregnancy at such an early stage?