Heartbeat at 6weeks 2days!!

Good morning ladies!!...I have been having horrible back pain and a weird pain in my lower pelvis!...so i finally broke down and called the dr yesterday and due to my 3 previous losses they sent me for an ultrasound. Which we seen the little peanut and the heartbeat was 120..is this a good number at this point? ...my anxiety has been through the roof lately worrying that something will go wrong!..but this is the farthest we have ever made it so im want to be excited but at the same time im scared to death! ...they also found a small sch (not quite sure about that) but I have to go back next week for another ultrasound!