I use it right after my guitar. Robert Keeley recommends putting it right after your overdrive, but since I don't use an overdrive (that's what the Road King is for) I just put it in it's traditiional place. This gives you a nice, full, sustain-y, even tone for the rest of your chain into your amp. Keeley also recommends, and I HEARTILY agree...do not put the compressor at the end of your chain or after delays or echo effects.
If I understand your signal chain correctly, you run your OD, chorus and delay in a loop, but a looper delay in the front of your amp....I would try a couple of different things.
I would go guitar...Keeley....OD...then the looper....and run my chorus and delay (in that order) in my fx loop.
You might want to try what Robert suggests and go guitar...OD...then the Keeley...etc.
Most players I know experiment until they find what they are looking for. Keeley does know compressors, tho, and I think all his suggestions sound good.
Good luck, and let me know what you find.
RB