Please, don't keep this from your mother. She needs to know, so she can help you figure out what the problem is. You'll be surprised, she may not freak out as much as you think. When I was 16 I had to tell my mother that I was pregnant, so I'm sure your mom will be thankful that you told her, because her main concern in life is to protect you.Im not a dr, but I am a mother and I would want my children to tell me what is going on in their life, so I can get them the help that they need. You do not need to try to handle your problems on your own. Take advantage of having a mother, who will help you. She won't always be there.
Please don't keep this from your mom. You need to sit down and tell her how you are feeling. I am not saying it's something terrible wrong with you, definately not as I think it may be something quite simple to sort out, but your mom does need to know - it's her job to share the worrying anyway! But I do think you should get your blood sugar checked - my 12 year old has a problem with low blood sugar and the symptoms sound the same and it only occurred when our diet had changed to a really healthy one - she doesn't seem to absorb the necessary sugar from her diet so she now has extra fruit etc in her school bag for a snack if she starts to feel wobbly or has trouble focussing. You can buy a meter to check blood sugar on ebay, from chemists and some supermarkets - they cost from about $20 (might even be cheaper than that!) then keep a check on it - you may find it's a bit low when you start to feel funny. But please talk to your mum.