Breast milk supply...

My kiddo is 10 weeks old and he is exclusively fed with breastmilk. However, my supply seems to have gone down quite a bit and I'm starting to worry.

I used to average about 4-6oz per boob per session but now I'm only averaging about 1-2oz per boob per session.

Also, I used to be able to stop my pumping sessions after 10 minutes or so but now I have to pump for about 20 minutes or so in order to get any worthwhile amount of milk from them.

Any suggestions as to how I can get my body to go back to producing more milk???