DIY enanthate vials usually have 40 mg / mL, so 0.15 mL should be 6 mg?
Using the injectable estradiol simulator, this is what levels would be estimated to be over time:
Notice how it takes nearly a month to even get to a steady state ... EEn has a half-life of 5 - 7 days, so it takes a week to peak and another week to eliminate. This is compared to estradiol valerate (EV) which has a half-life of 3.5 days, so EV peaks faster and higher, and eliminates much faster than EEn.
When I first started EV injections, I could feel changes the night I injected, but I didn't feel any obvious benefit or mood change until the third day or so.
But it's important to note that not all trans women react to estrogen the same. Some feel no difference at all. Others actually have worsened dysphoria.
So early on you are not likely to notice many physiological changes. In my first month or so of HRT, the earliest changes I noticed were softening skin, changes to body odor (less spicy / less smelly), and fewer involuntary erections overnight and in the morning when I wake up. I wonder if you will start noticing these soon, too.
EDIT: I had sore breasts pretty quickly, too - I think it was a matter of weeks, but I was taking EV which brought my E levels up quickly. I would expect breast soreness in 1 - 3 months with EEn, but I'm not certain - I bet others have written about their experiences starting with EEn.