2015 after replacing battery I failed to reprogram or rest key fob NOW it's In abd out if anti theft mode abd will not start at all

[TiffPeyWes]

It started with occasional go to crank my car abd it would not turn on at all. Checked battery and the battery was not connected properly meaning (not tightened and wasnt grounded properly. After fixing the battery connections the SUV seemed to work fine till a week maybe two weeks later and it would not start . Radio, lights all were working also key fob was not unlocking the car . Replaced key fob battery. Wasn't aware I needed to needed to reset / reprogram my key fob. Even tho I didn't reset the SUV it would go a couple days be fine then it would do it all over again . on top of that RT before this happen ( no start)+ when I go into reverse and put the car in drive it will go dead on me but will crank right up in neutral. So I done the open door with key, hold down unlock oncar door and hold down unlock on key fob while symotamous putting key fob in ignition until doors engage. When I done repeat process the car said theft in progress and anti theft light stayed solid. Now the car will not do anything . Ther antileft light is off and in the past few hours I've been able to crank it once but only after replacing the battery to the car with a new one drive it three miles and now three hours later it's back to no start .!! Need help! Computer is not spitting out codes .