Had Unprotected Sex, On Birth Control Tri Sprintec And Antibiotic. What Are Chances Of Pregnancy, Advice?

Hi. While having sex with my boyfriend last night the condom broke when he ejaculated. I am worried about the possibility of pregnancy. Here is the situation. I am on birth control (Tri Sprintec), but also on an antobiotic to help with acne , and I know that it s use reduces Tri Sprintec s effectiveness.I checked fertility awareness methods and have come to the onclusion I am not ovulating. Also, the reason I noticed it broke is because a lot of his ejaculation was running down my leg. I immediately washed everything. I cannot afford Plan B. So, here is my question. Based on what you ve heard, what are my chances of becoming pregnant (I understand this is just an eduated guess)? And can I use an elevated amount of Tri-Sprintec as an emergency contraceptive or simply stop taking it to induce a period?