Ok - If you did conceive a week ago, you wouldn't have that much going on this early. It's more then likely mostly in your head as hard as that might be to hear. Trust me... Secondly you are really young!! I had my 1st when i was 17 and it was no piece of cake! It's hard, i had to drop out of public school, because i couldn't keep up and was so tired and had morning sickness so bad. I did end up finishing when he was born by homeschooling, but you miss out on a lot. You still have you whole life ahead of you. If i could go back, i would keep things how they are right now but just push it back a couple years, So i could graduate with my class, go to college, have time for myself to figure out who i wanted to be and who i was going to be without having the duties of being a mother to. Right now you might think you know what you want and you might think that you don't care about those things, but 7 years down the road you will wish like hell you had thought twice!! It's not about you and the boyfriend anymore, its another human being that you have to take care of. IF you can't afford to get a pregnancy test, how are you going to buy diapers? or wipes? or clothes? or bottles? A baby needs so much ALL the time and not just love and taking care of, things you have to buy. They grow so fast you will have to buy clothes every couple months.
Maybe sit down and talk with someone a little more before bring a precious baby into this world when you are still a baby yourself!!
BTW - you can get pregnancy test from the dollar tree, and usually all stores have their own brand that are cheaper then name brand.