Two PT fails in 3 years?

I have a PT test in less than a week, I have been running and doing push-ups/sit-ups but it's sometimes really hit or miss for me. I tested myself on sit-ups/push-ups the other day and got 53/40 respectively but I just tried today and struggled to hit the minimums. As for running I have always struggled with it and have been having a hard time just practicing the 1.5 mile.

I failed a PT test almost 3 years ago, got put on mando and then scored 90+. I'm really worried I might fail again. What happens if I do? Will I be ineligible for promotion? Would I be eligible again when I pass?