Misleading cramping, anxious mama

Anyone else start having menstrual like cramping for a period of time and some lower back pain and think, “this is it, this is it” and then it just goes away lol 😂 now I am 37 weeks 4 days I guess I should at least want to get to 38 weeks I am so tiny that sometimes I’m scared my baby isn’t gonna be big enough but my doctors always have their measuring tape and say, “you are right on target!” Lol all I know is my baby was in the 52 percentile at my 20 week ultrasound they don’t do anything else to let me know the weight now. I have gained about 30-35 lbs and we all joke because we don’t know where so I am hoping that means baby will have some weight.