Jaki - I expressed for 6 weeks before bub got the hang of attaching, and he's still feeding now at 3.
It will get much easier if you can express enough to be one feed ahead. That way you can try to attach (put a 5 minute limit on it), give the ebm if needed, and express once bub is fed and settling (my ds found the pump noise quite soothing).
Bub will grow and get the hang of it - in the meantime expressing will keep up your supply and ward off the mastitis monster, and also ensure that he gets fed.

It is also very possible that bub will find it easier to attach to an emptyish boob - so try expressing and then attaching (and then give some of the ebm back to bub) as well.

Congratulations!