will i get a criminal record for 3 train fines?

ive been fined for not paying for a train ticket 3 times as of today. the first i just payed (i was 16 and just got on a random train with a friend) but the second one i appealed because the train conductor usually allowed us to pay for tickets on the actual train and then the fine was just sort of sprung on me and a few other students on the same train. today id brought a ticket, but i didnt realise my railcard had run out a week ago. i told the person that id only recieved one fine before because i forgot about the first one, and she warned me that a third fine would go straight to criminal prosecution, so now im scared im going to get a criminal conviction and that it could affect my university offers? does anyone have any experience with this situation/ what it intails?