you probably have heard this a million times already, but try to relax--physically and mentally.
if your focus now is to reduce your reliance on physical/external strength, try shifting your training priorities from successfully throwing or manipulating uke, to simply connecting
to their centre first. once you have them connected, move your centre
, not theirs, and see what happens.
try and look at some videos on 'atari' and/or 'musubi' type exercises. Endo Seishiro has some pretty good DVDs on that. having said that, watching is one thing, feeling is another. find someone at your dojo (or elsewhere) whom you think moves well, and is very powerful without using 'strength', and feel what they do to you as uke.
good luck! ...and relax.