Yep, I can definitely relate. I am disgusted by myself (always have been), but sometimes I do take an extra effort to look pretty, usually to no avail though
I don't have any advice, but when I have one of those self-deprecating moments I think about something that an old friend once sent me when I was telling him about how ugly I feel. It usually makes me feel a little bit better and I hope it can help you too

I will translate it and write it here.
... Did you know that ... ?
- if the manequinnes in the shop windows would be real women, they couldn't have children because their hips would be too narrow
- there are 3 billion women in the world who don't resemble at all a super top model and only 8 that actually are super top models
- Marylin Monroe was a size 42 and the size 42 of those days corresponds to a size 46 of our days (Italian sizes, I don't know the US equivalent, sorry)
- if Barbie were a real woman, she could only walk on all fours because her proportions wouldn't allow her to stand up straight
- the average woman weighs 66kg
- 20 years ago top models weighed 8kg less than the average woman, nowadays they weigh 23kg less
- the models we see on magazines are photoshopped and actually look very different from the impossible standard of "beauty" those ads are setting
- a survey taken in 1995 revealed that 70% of women feel depressed and guilty after reading a women's magazine