Hello this morning i've woken up and then about 10 mins later when i got up i had a awful pelvis and lower back pain it was a achey pain and its happened multiple times i have bad constipation so i'm thinking could it be trapped gas?

Need examination: I don't believe that simple "trapping of gas" is the most likely cause for your symptoms though being gassy can be uncomfortable, no doubt. I believe you should be examined & a good dietary history along with bathroom habits should be obtained. You may also benefit from a urinalysis. Fixing the constipation problem certainly could help you even if it doesn't fix the symptoms.