Wanting to be Air Force Security Forces?

Hi I already swore into the Air Force DEP but havent got a job so most likley I will be going in to basic as open genral which is fine with me despite all the talk about not doing that...But I really want 2 do SF now but at MEPS I asked the job counselor about why people always say if you go in open general you get SF then he said dont worry about that you will never be SF you didnt lift enough weight..Back then I didnt want to do SF now I really really want 2...That was 4 months ago and ever since then I've lost about 20pounds and PT everyday so I can almost guarentee I can lift enough weight..Is there anyway I can do it again?Or maybe in BMT talk to someone about lifting the weight their so I can be SF?Any help would be great thanks!