Okay if you are under 5 feet tall then you are prolly not going to like the ergo. From my investigations it seems that it does not suit well those of use who are hmmm shall we say vertically challenged. This is advice from several babywearing forums. Their advice for shorter people is the patapum, or catbirdbaby style of meitai type carrier.

As for fitting it, To reduce the stress on yur back, babies bottom needs to be sitting higher than your belly button so you could try adjusting for that.

I do know what you mean about the straps cutting under the arms, I had the same problems when I tried it on and I am 5 foot 1inch on a good day.

Good Luck, I have a feeling a trade in might be on the way...hehe......