You sound as though you might need some additional time to get through your class. It is very important that you reach a point of feeling comfortable and relaxed while using a regulator, before you end up in open water on one. This might require a whole pool session spent in shallow water. You could begin with using the regulator like a snorkel (in other words, floating on the surface of the water, breathing through the reg, so you aren't even underwater, and all you have to do is lift your head to be breathing ambient air). Or you could even stand up in the water and just put your face in it with the regulator, until you are convinced it is going to work and deliver gas.
What's critical is that you not push through while there's still significant anxiety. Scuba is an amazingly safe sport for something that's carried out underwater, but what is very often involved in accidents and deaths is panic, which is anxiety spiralled out of control. It may be that nereas's approach of freediving first would be a good one for you, although a lot of very confident and competent divers don't ever free dive. Maybe watching some dive videos and visualizing yourself as the diver, floating through beauty, might help allay your worries. But somehow, you've got to get past the anxiety, because it, itself, is dangerous.
What's critical is that you not push through while there's still significant anxiety. Scuba is an amazingly safe sport for something that's carried out underwater, but what is very often involved in accidents and deaths is panic, which is anxiety spiralled out of control. It may be that nereas's approach of freediving first would be a good one for you, although a lot of very confident and competent divers don't ever free dive. Maybe watching some dive videos and visualizing yourself as the diver, floating through beauty, might help allay your worries. But somehow, you've got to get past the anxiety, because it, itself, is dangerous.