Hi, I filed my taxes electronically using my last paystub for reference. When I received my W2, my total income was less. I guess my taxable income did not include my health insurance. I reported the whole gross amount. I don't want to wait for my refund but if I amend the claim, I will get back more money? What should I do?

You have to file electronically through a service. Go back to that service and enquire how to amend your return. In the future, don't be so impatient, wait until you have received all the official documents before filing.

Once a return is filed electronically, it is filed and cannot be changed or re-submitted.

You need to file Form 1040X to amend the return. However, the IRS MAY fix the problem for you without you doing anything. Wait until April to see if the IRS adjusts the return for you. If they have not done it by April, they are not going to do it. You can amend then.