I agree this is a highly personal decision that only you can make. Weigh things carefully as I have seen all three choices chosen with both positive and negative outcomes. You need to picture yourself 10 years down the road and contemplate your feelings.
Of course it comes down to one of three choices
1) abort
2) adoption
3) parenting
I noticed the Australian flag next to your name.
Have you considered contacting some of the unplanned pregnancy support groups (pro-choice and those that assist in adoption or aiding the expectant mother in seeking financial aid and care) in your area?
Such as..http://www.childrenbychoice.org.au/ ((please note I am not 'endorsing' this organization as I am not personally familiar with Australia but similar groups can be very beneficial in supporting you through this deciding period)
I know it is hard and the feelings swing to and fro......just breathe and discern your own heart. When you close your eyes in the moments of peace which scenario brings you the most satisfaction.
I am curious though why your BF is 'assuming' what he is assuming? Has he stated his feelings directly on the matter?
Sending you warm hugs of reassurance in this moment of uncertainty.