I got pregnant at 17 just after getting full marks in my A Levels, had no boyfriend, was planning Uni etc and I managed just fine, despite it totally not going to plan..so I'm not scared of anything like that.
My reason for waiting is purely because we have spent over two thousand pounds on a holiday in June and I wouldn't want to go pregnant as I went to the USA pregnant last time and ended up in the hospital etc and it was a scary experience. If for some reason the holiday got cancelled I would 100% just think who cares about losing weight and just try, its taking so much will power to wait knowing my OH is the one instigating the baby making. The back of my mind is scared he might change his mind in 6 months time!