Switching birth control pill and estrogen dose

Hi, I have been searching the internet and there is absolutely no information on switching from higher doses of estrogen to a lower dose. My doctor is didn't mention anything about how to switch, and is now out of town.

Background: I have been taking a combination birth control pill for about 5 years now. I am absolutely religious about taking it at the exact time each day down to the minute. I am currently not on any supplements/ drugs, besides a multivitimin which I take at the opposite time of day from my pill. I do not use a back-up method of birth control and my partner, who usually withdrawls recently did not (about 4 days into my new pill pack).

I have switched from being on nortrel 1/35 for about a year now (because of side effects), to a triphasic estrostep generic. I am concerned about the innitial effectiveness of the new pill because instead of starting at 35 mcg of estrogen I am starting on 20 mcg (will my body be used to the higher dose and cause me to ovulate)? I started the triphasic pack at the time that I would have started a new pack of my old pills ( on time after inactive week). The package insert doesn't have any information on switching brands.

Should I be concerned about pregnancy?