Hi, I am also 5'7 small frame 130-135 depending on the week and what I eat. I conceal a Glock 19 just fine on myself using Med T-shirts or small polo-collar shirts.
Hope that helps. If you want deeper concealed go for a Glock 26. I wear bootcuts and place the 26 on my ankle/docker pants/jeans, and the 19 on my hip just fine with tuck in shirt/polo/collar shirt.