My mortgage keeps going up - dumb it down for me please

So we bought a house 3 years ago. Our mortgage about was $1,300 we are now paying $1,716 and we are honestly over it.

It is a fixed loan. After the first year we got a letter there was a huge shortage (4K) in escrow because the value of the property was going off of only the land not the house (yet) since it was a new construction so we basically were paying too little. We payed the huge 4K hit and the new mortgage was $1,666. We finally didn’t have a shortage this year and I just logged in and it increased by almost $50. WHY

Can someone explain this to me? (Will be calling my loan company tomorrow) but will it always go up???

I was under the impression that property taxes and insurance are the two things that would warrant an increase but there was enough $ with the 1,666 prior mortgage...