How should I behave??

8:30 - Victoria Line towards Brixton.

Always overcrowded, even though the trains go every 1 minute!!

I got on at Euston. I was stuck between the door and someone's back till Oxford Street, trying to catch something with my right hand. Needless to say, there's no air-con in the underground! What for? ;) Drops of sweat were falling gently down my back... They were tickling me. Later, although it was still very crowded, I managed to move to a more secure place. Was it really secure? Well, at least I could hold the railing, facing the plastic glass that separates the seats from the doors. There was a guy standing behind me...
Now when I think about it, I feel quite scared but maybe I shouldn't take it so seriously...?
He was pressing my body with his from Oxford Circus to Victoria (it's where he got off) . I didn't feel comfortable about that so I tried to move closer towards this glass but he was right behind me all the time... Even when the train was stopping and, according to natural laws of physics, he should move in opposite direction, he was always too close, pushing himself into to my hips...
I've never had such situation before. I just didn't know what to do. Gosh, I took assertiveness and self-defense training for women and why I felt so paralyzed??