how can i be more feminine

I guess it depends on what you mean by "being feminine". If you want something gender-affirming but subtle, you can try a few things like getting a sort of girly haircut, or letting your hair grow long. You could paint your toenails; people may see them if you go barefoot, but as long as you wear socks around people you'd be the only one to know. You can try getting some women's underwear, since that tends to be easy to hide. I also have a couple shirts that aren't too girly-looking, so I could wear them in public without anyone but me realizing that they're girls' shirts.

 

Panties, unpadded bras, and women’s tanks are a good way, though if laundry is communal, you may have to take your “girly wash” to a laundromat.
Women’s jeans often fit much better, and often are far less “baggy.” Just tell your parents that you don’t like the bagginess of men’s jeans.
If you can, grow out that hair. If that’s not an option, like solarcat said, getting a more feminine haircut.
You could paint your toenails colourful and use clear coat on your fingernails.
If you are able to, a nightie to sleep in would be good.
Deodorant/antiperspirants/perfumes: Women’s ones have just the same ingredients and strength as men’s, the only thing different are the scents(the new line of Old Spice notwithstanding), so if you can sneak a tube into the shopping cart.
Pick up some “feminine” mannerisms. Observe your mother, if you have sisters observe them. See how they do certain things and mimic them.
Cross your ankles, not your knees.
Keep your knees together, or at least no further apart than a couple inches.
While around people who aren’t your family, talk in a higher register.
Yes, it’s a lot of little things, but they build up.


It also sort of depends on how your family is. I know that when I was younger, and still living at home, my “peculiarities” would get me in trouble. I’d put on a bra at night, and would fall asleep in it, and would then get in trouble in the morning. However, this became less of an issue as I got a little older, as in 2014 I started wearing a cute nightie to sleep, and my door would be open. I know that my mother saw It, and I’m glad she didn’t comment.