I had similar results; I used only patches and my T levels were in the lower end of the cis female range at the 3-month recheck. Estrogen *does* lower testosterone to some degree. Essentially, E IS a T-blocker, but it generally isn't enough by itself unless it's taken in dangerously high doses. But for those of us who are especially fortunate, it's enough by itself. I was grateful I didn't need to take another drug.

(I was on a super low dose of E, too.)
And I had fantastic results, if that's any reassurance; by six months on patches alone I couldn't pass as a guy even when dressed as one and I was 42C.