Assuming both of your names are on the deed, and on the mortgage loan, you will each claim the amounts you "actually paid" with your own money on your individual tax returns.
You and your BF can enter the amounts you each personally paid for the mortgage interest, property taxes and loan origination fees (if any). And of course, if you are not married you cannot file a joint return. Some information on what is deductible for home ownership:
Home Ownership
There is not a first time home buyers credit on a Federal return. That ended in 2010. If your state has such as credit, you will be able to enter it when you prepare your state return.
Buying a home is not a guarantee of a big refund. Your deductions for homeownership combined with your other deductions (if any) must exceed your standard deduction to change your tax due or refund. If you purchased your home late in the year, you do not even have a full year of home ownership deductions.
Go to Federal> Deductions and Credits> Your Home to enter mortgage interest, property taxes, and loan origination fees (“points”) that you paid in 2016. You should have a 1098 from your mortgage lender that shows this information.
Your closing costs on your new home are not deductible except for prepaid interest, prepaid property tax or loan origination fees. There are no deductions for appraisal, inspections, title searches, settlement fees. etc.
Your down payment is not deductible.
Your homeowners insurance for fire, hazard, flood, etc. is not deductible for your own home.
Home improvements, repairs, maintenance, etc. for your own home are not deductible.
Homeowners Association (HOA) fees for your own home are not deductible.
https://ttlc.intuit.com/questions/2900844-where-do-i-enter-my-1098-mortgage-interest-statement
But unless all of your itemized deductions exceed the standard deduction there will be no tax advantage to claiming it at all. In you case all itemized deductions must be more then $6,350 to have a tax advantage.
For 2017 the standard deductions are:
Single or filing Married Filing Separately - $6,350
Married Filing Jointly or Qualifying Widow(er) - $12,700
Head of Household - $9,350
(If over 65 or blind add $1,250 - $1,550 if filing single or HOH)