Actually it is not testosterone that affects your frame, it's estrogen.
I doubt at 18 it matters though.. estrogen stops bone growth, at 18 I think males usually stop bone growth too.
My boyfriend was 183 for years now, he is 20 years old.
I didn't grow over 164cm for years either, probably stopped growing in height since age 15 or 16.
I started estrofem and spironolactone at age 19, I got to about 34B/32C after 3 or four months.
then I had to stop estrogens (I won't explain) for a bit over than a year, I am not sure if I was on it for 3 or 4 months.
Now I started it again, about one month ago, still no changes in breast, no feelings there either.
I am really scared I damaged the growth somehow and I really hope I didn't.
Without cloths, the breasts don't look big, it's mainly push up bra that can make them look quite (QUITE!) big..
People don't even notice I have breasts unless I tighten the shirt or wear a tight shirt.. but I don't like tight shirts, I have a LOT of fat at my waist, I was quite fat 90kg and now I am 63kg and if I wear a tight shirt I look really fat.