Can parents tell that their child is pregnant? Because my mom is looking at me funny like she knows something.

Parental Intuition. If you have a pregnancy bump, then she might have a visual reason to be suspicious that you are pregnant. Also, parents have a good sense of who you are and can easily pick up and sense changes you may not even realize that you are exuding. They may not know exactly you are pregnant, but they may pick up on the fact that something is going on with you..
Moms know. First of all are you pregnant or not? My experience tells me that mothers can tell anything and everything about us. She may be noticing little things you say or do and having been through this herself she may notice early changes. Talk to your mother, she can be a big help if you are pregnant.