Is it that you want to look feminine, or that you want to look sexy? I mean that honestly, not rudely. Because there are lots of women who aren't typically feminine that are sexy as hell.
Sexiness is all about confidence. Right away from your post you seem to be a little uncomfortable with your clothing and maybe some aspects of your appearance. I agree, work on losing the weight. Not because you need to be thin to be feminine, but because you'll carry yourself differently if you feel good about yourself (not to mention that it's better for you, which you obviously know).
Secondly, do you have a friend that you can go shopping with? Go shopping and try on things that you like but would normally say "I'd never wear that." Why not? Just try it on. Maybe it will look amazing, Maybe it will look rediculous - you can always just put it back on the rack. Believe your friend if she says it looks good, and commit to wearing the new clothes. I have been working on changing my wardrobe for the past couple of years, and I cannot even begin to tell you how much better I feel when I look "put together" (and I wear jeans almost every day, even to work. You can look very stylish without wearing a gown), Don't worry about covering up the tattoos, or anything like that. You just find an outfit that makes you think when you look in the mirror "I'd like to be friends with a person who looks like that."
Same thing with make-up. Maybe you put on a touch of mascara, enough that you feel it makes a difference, and see how differently you interact with people throughout the day.
Invest in some nice underwear. It's hard to feel sexy and feminine with drooping boobs and ratty cotton underwear. I got some new bras at nordstroms a couple of years ago, and I swear it changed my life. I no longer felt like an old frumpy mom, but someone who could rock her curvier look.
None of this has changed who I am in the slightest, and it won't change you, except for the better. Good luck!