Hi first, if your only income is 428/month, yes, I suggest you apply for SSI immediately. I say immediately because SSI pays NO back benefits prior to the time you apply. You need NOT prove illness or disability, only that you are poor enough.
Secondly, if you are paying SS taxes, your income is being reported to the SSA each year. Usually there can be a delay by 1-2 years in it being reflected in your benefits if you are warranted an increase because the figures first go to the IRS when you file your taxes, and then to the SSA. But as I understand it, the current years (lagged) calculations are not done a la carte, but in batch.
To find your SS deductions from your BVTC checks, you can look at your paystubs - under FICA. For 2016, it was a 6.2% tax from your wage, so you can also take your gross for each paycheck and apply the %.
In addition, you can go to
to get your estimate of SS taxes paid (and Medicare taxes paid).
If the above don't work for you, than unfortunately you will have to go to your local office and ask in person. But the link works for most people so long as they can answer the questions to prove identity.