Your college LGBT+ representative, or a postgraduate representative, may be a good starting point if you want to discuss any issues about sexuality and gender.  You should be able to find their contact details by searching for [college name] MCR on the web.

The LGBT+ Campaign supports LGBT+ causes and looks after the wellbeing of all LGBT+ students at Cambridge. They run frequent events including game nights, LGBT families meets, tea and coffee. They also offer one-to-one advice by email, phone, or in person.