A heart-rate monitor is a must when increasing mileage IMHO.
If you don't have one it's easy to settle at a pace than is just a little bit too fast to manage your volume goal for the week.
SO get a HRM, find out your MAX HR and stay below 70% for all your runs, that means slowing down in uphills. Average HR during the week should be about 65-66% if done correctly.
Btw have you ever thought about setting training goals in terms of HOURS rather than in miles. A 10 hour goal per week is pretty hard but a bit easier. Instead of chasing miles you are chasing minutes. That means that speed doesn't matter, you won't get more minutes if you run faster.
For an elite-runner: 10 hours = 100 MPW (Lydiard-style)
If your ultimate goal is 100 MPW you might have to spend 13-14 hours at the same intensity as the elites, it doesn't make any sense. Consider setting your training goals in hours.
The good thing is as you improve you will cover more miles in your 10 hour week. In the first week you might cover 80 miles and after two months 90 miles.