Heart beat

Hi ladies. Quick question for you. Have any of you bought the fetal heart monitors?  I've been having some cramping and the dr says that normal but I didn't have this with my first child nor did I have nausea like I do with this one. I'm about 11 weeks along and the dr says I can come in for a heart beat check but the first appointment they have isn't until next week Thursday.  I need to know my baby is ok. I was wondering if the over the counter heart beat monitors really work ?   I'm scared and don't want anything to happen to my baby I just need to hear the heart beat so badly especially with this in and off cramping and it moves around so it's not in one spot and no bleeding but I'm so nervous. Any suggestions ladies?  Thank you so much 💜😀