Should I be concerned and am I "upside down" in my mortgage?

I purchased my home in 1999 for $79,900.
With property values decreasing, I’ve gone from $102,000 value a few years ago, to $58,500 last year, and $49,900 in value this year.

Based on value, the taxes are lower so of course my mortgage payment is lower. Last decrease put it down to $577.

So if I can continue to make the payments, does it matter if I am “upside down” in value?

I think apartment rent is higher than my mortgage. I shouldn’t have to move, should I?