New Company: Lots of Girls

Hi J,
I'm from Rio de Janeiro and I've just started in a new job position, in a new company, where there are a lot of people younger than I am (I'm 30 years old and the others are usually from 23 to 27). I was used to dress regular, not fancy, but in this new opportunity I started to get disturbed by the way I look, the way I dress, the way I present myself.

I don't wanna look bad in front of the company's women staff, but I also do not want to spend a lot of money on new clothes. By the way, I used to swim and cycling, but because of a problem in my knee and the end of my masters, I put on 35Kg, so most of my old cool clothes won't fit, so I have two problems hanging around in the company, the "chubbiness" and the clothes (that I buy from time to time only to fill this new body shape, only the necessary)...what do ya think I should do?

Thanks!