Yup, we did the bedside-cot arrangement too (clingy DD didn't actually lie on it, but it gave extra arm space for me and protected her from falling anywhere) and feeding from same side. To feed from right breast on left side I just scoot back an inch then lean forward. I must admit at three weeks we probably weren't in the swing of easy night-time feeding - DD used to root around and not find the nipple right in front of her! and I slept with a nightlight on so I could see what I was doing for about a week! It will take time to settle, but you'll get there.
Eventually we moved the cot to her own room, where we put her to bed in the evening and used a guard on our bed where she spent the second half of the night.
Just remembered!! We had a King Size Duvet even with a normal double, so I used to flatten that down in the middle of the bed and put DD on top of it when she was small. That way we both had plenty of duvet either side (no danger of pinging her off!), but it acted as a sort of natural barrier for DH. That helped a bit.
Also, DH put his pillow overlapping his bedside table so he could lie a bit further away at a bit of a diagonal!
When she got bigger I didn't worry about her being in the middle so much, but it became a squeeze because she would sleep sprawled out, taking up as much space as DH does, leaving me with about 3 inches
In the end though we bought a King Size bed, and a single bed for DD in her room when she was about 18months, so if need be I could sleep with her in that.
I remember feeling nervous about the whole thing, and frustrated that no-one could give me the simple, cure-all formula for how to safely fit three people in a bed made for two (lots of matresses on the floor would have been fine with me, but not DH) - but it turns out everyone just wings it