My boy went through the same stage hun. From 3 to 12 weeks he would only sleep on me. If I put him down, he'd last 10 minutes max. It was freaking exhausting, but it did pass.

Now if he sleeps for too long in his cot, I miss him and can't wait for him to wake up.

When I was in the middle of it, I would hate it when people said 'it will pass' and 'it won't last forever' because I couldn't see how it would ever end... But it did.

He still doesn't self-settle, but I honestly dint try too hard and absolutely adore seeing his little sleepy eyes close as he drifts off in my arms.