I swear I can feel movement

Stephanie • im 26 and have 2 amazing kids with my ex. i just found out im pregnant with my rainbow baby by my boyfriend of 3 years due December 30
I'm 15 weeks and 1 day. This is my 3rd baby 4th pregnancy. I swear when I'm laying down on my back I can sometimes feel one side of my lower belly become very hard. When I touch my stomach its hard and I touch the other side its normal. I swear my little one is moving around in their lol I find out next Tuesday what I'm having and I can't wait