Can I sue my mortgage company? - 1

So long story short… We built our own home 10 years ago, at the time the economy was good, approved for a super loan $1,000,000. At the time business was amazing and we thought we would be able to pay it off in 10 years max, but then the economy crashed and since then it's just been a lot slower but recently business is really bad and money is tight. Tried to get a modification was denied and now in process of appealing for an extended loan. However we are really struggling and don't want to go into foreclosure, almost did last month. So we went and spoke to 2 different financial advisors about our options and what we should do. Both said the same thing, our mortgage is not adding up. The amount we are paying each month is not right, based on the principle, interest, and time. It is almost $800 more than it should be. They said we should speak with the company and double check and if we are correct we have a very good case to sue them.

So how do I go about this? What type of attorney should I speak to?

Any help or advise is much appreciated.
Added (1). It was calculated with all the tax and insurance and all of that. This company is not that great with calculating things. On the first attempt to modify they calculated income completely wrong. So I wouldn't be surprised if this is wrong too. That Is why I am asking

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