Hi,
How are you?
Your symptoms seem to be the result of hormonal dysfunction. Milk discharge from the breast is most likely due to secretion of prolactin. Prolactin is secreted from the pituitary gland. Prolactinoma, certain medications and excessive fondling of breast can lead to a milky discharge.
I would suggest you to consult an endocrinologist at your earliest.
Discharging breast milk and abnormal menstrual cycles is suggestive of a pituitary gland problem, particularly, a prolactinoma--which is a benign tumor that sits on your pituitary gland in your head, and secretes excess prolactin, a hormone that controls the production of breast milk. This isn't life-threatening or anything to be really worried about, but you should see a doctor and they will likely order bloodwork that includes a pituitary panel and a thyroid panel, and order an MRI of your sella tunica (where your pituitary gland is located) to look at your pituitary gland and identify any potential abnormalities. Your GP might refer you to an endocrinologist right off the bat, too.
I have some MRIs of my pituitary gland posted under my photos in my profile, if you're interested in taking a look at them. Initially, it was thought that I had a TSH-secreting tumor on my pituitary gland, but it turned out that my pituitary gland was fine.
The lump under your left armpit is probably a swollen lymph node, which is indicative of infection and likely nothing to worry about at this point in time. Lymph nodes swell all the time. If it's very hard and it stays like that (or gets larger) for longer than 3 - 4 weeks, that's when you should become concerned.
Good luck and I hope you feel better soon!