United States Marine Corps!?

hey Friends! so i just DEPed in on the 3rd and im SUPER MOTO and waiting to ship to MCRD sandiego..i just need some advise..I have been front loaded at my recruiting battalion and i get first pick at any spots that open up this summer so i dont have to wait until December..my problem is i am a high risk recruit and could only p 2 of the 3 IST (ive lost 70lbs to enlist so i have no upper body strenght) I am not to worried about meeting ship weight i can run weight off over night its not hard(Oorah!) but how can I effectively learn to do Pull ups within the next few weeks? so im prepared when a slot opens too boot?....Thank you Semper FI!