I always had gynecomastia, but my right breast was clearly bigger than the left.
On the first week of HRT (probably on the third day), my nipples started to get a bit swollen.
After one month fat started to deposit on my breasts and they started to grow in size (the right one still a lot ahead).
On the second month I could notice a small lump behind my nipples and, oh my, they did hurt when touched! I had to learn to avoid sleeping with my back up!

On the third month the lumps got bigger and my nipples and areolas increased in size.
On the fourth month my left breast grew a lot and now both my boobies are almost the same size. They got clearly noticeable and it's been hard to hide them, mainly because they just love to swing around when I walk

On the last week (almost 5 months) I noticed that my right breast is getting a tubular shape. My areolas are huge (around 5 cm) and, after measuring, I concluded that I am with a 38B cup right now.
Just remembering, breast growth don't follow a steady line. You can pass days without noticing anything and, when you are starting to get concerned, suddenly they decide to grow!
Good luck to you