I've become so claustrophobic that I can't close te shower curtain whenever I have a shower, how can I help this?

Efficient treatments. There are several techniques that can help resolve phobias. One of the most efficient i've found is energy psychology that involves tuning in the phobia and tapping at specific locations on your body. Read about it in energy tapping. Otherwise you should consider seeing a therapist who specializes in treating phobias.