I entered my mortgage 1098 info on my rental income; should I have also added it in deductions? I feel like it's counting it twice.

For two separate properties, do not enter your 1098 for your rental as a personal Schedule A, itemized deduction.

If you rent part of your personal residence:

Mortgage interest and property taxes are divided between personal (Schedule A, itemized deductions) and rental use (Schedule E) , proportional to the number of days used for each.

For instance, if you rent out 40% of your floor space, deduct 40% of your property tax and mortgage interest times days rented /365 as a rental expense, and 60% of the property tax and mortgage interest as a Schedule A, itemized deduction.

So, if you are renting out part of your personal residence, you will enter a portion of mortgage interest and property taxes in both areas.