I'm 5FT 8" and weigh 147lbs (Welter weight) and I'm one of the shortest in the gym I train in. In sparring I always end up chewing a few punchs when I get in close but I'm getting better, work on your footwork, slipping and timing. I usually wait for my opponent to over commit his jab and then try to duck under and get inside, once I'm inside I let a barrage of punchs go and then let a final jab loose as I duck and pull out again.

Being shorter is both a blessing and a curse but working alot on your defence and parrying will mean the difference from eating a few shots on the way in and getting in clean.