Don't worry about it Lupita. Scuba is a unique sport.
It's the only sport where you have 360 degrees of free movement in all directions. The amount of information your brain needs to process to maintain and understand where you are in the water column is enormous. The amount of situational awareness needed to comprehend all this is something that will never come natural to us.
Because of this it's completely understandable for new divers to be overwhelmed. What's going on with you is that you're stressed, we all were when we started. The difference is how we handle it. Some people take to stress really well and are able to muffle it, others aren't.
In the end though if you spend more time in the water it'll become more comfortable to you. Its like being afraid of the dark. The more time you spend in it, the less scared you'll be, the more you'll realize how there's nothing to worry about.
Definitely talk to your instructor and ask if you could take the pool session at a reduced pace. If he/she is a good instructor, I'm sure you'll get some extra pool hours to get into a comfort zone under the water.
Bottomline, if you truly want to do this, you'll get over this fear. It will just take time. Be patient and keep trying. Take wee little baby steps. If it just means sitting at the bottom of the 3ft end on scuba, do it.
Or if it means floating at the surface on scuba, heck do it.
Feel free to drop by the Norcal sub-forum. We'd love to have you there.
Norcal Forum