Horrible back pain and light cramping

So since yesterday I have had horrible back pain then this morning the light cramps started. I never experienced this with my last pregnancy so I was alittle concerned and called my doctor who wanted me to come in for a U/S I'm 7 weeks and 3 days and was suppose to go in for my first appt next Wed. After about 20 sec my U/S tech told me to breath everything was fine she was just going to do some measurements and then turn the screen for me to see and hear babies heart beat when she turned it she asked if I knew what i was looking at I looked at my husband then back at her and she said yup there's 2!! OMG after a year of trying were having twins I never imagined!! My heart is soo happy