Congrats and welcome! IM is a great way to shift your chemical balance. It is effective and easy. I am on transdermal and my endo and I discussed IM a few weeks ago to get away from having to fiddle with patches all the time. She listed it as the 2nd most convenient application (next to implant) as you get away from daily dosing and the also pointed out that IM is capable to getting numbers really high in short order...but is has the downside of peaks and troughs. You might experience some moodiness as you near the time for your next injection.
No matter what method you choose, you will have clinical effect with transitional dosings. You can expect fatigue to set in for a little while as your body and mind transitions over to a new chemical makeup. Probably going to deal with that for a few months before things settle out. Breast tenderness comes on at about month 2 and then can come and go in a cycle, or stick around for what feels like months on end (my experience so far). As your true breast structure develops, you will feel them get hard masses, then soften and fill before starting back in to the cycle again.
I am basing all of this on observation and personal experience. I have many sisters that are at or beyond my current point of HRT. Some with less time have more pronounced development while others with much more time have markedly less...how our bodies react to being thrown back in to puberty and (for MTF) preparing for child birthing is very individual. Again, the main thing is to enjoy the experience as we only get to go through it this one time! It is truly amazing, the changes that will become evident. The biggest changes though, and all my sisters agree is the internal stuff!
