Am i a pushover?

im 19 years old and been with my boyfriend 2 years now. these past two years have been very difficult, he works in the british army and we dont live together so its abit of a distance but when we have the time and money we see each other and have a great time. about 4 months into the relationship he asked me to use his email to reply to an important message, i saw an email with pictures and videos from a girl doing well you know!... we spoke about it and i almost ended the relationship but we sorted things out and moved on, at the 7 month period i found my laptop browser history with a webcam site and it automatically logged in and there were obscene messages, he says it was an accident. so we move on... at the year mark he went to meet his ex at her house and didnt tell me when i thought he was elsewhere. she then told me and he said he wanted closure, so i flew off the handle but i had good reason to. and recently one of his closest friends told me that my bf told him he met some girl on facebook and went to meet her for coffee, i confronted him about it but he doesnt see how hes in the wrong, i dont understand why he feels the need to lie to me and go looking else where our sex life is amazing and we talk alot but i just dont know if im enough as im getting mixed signals because hes talking about getting married, how can i marry someone who cant tell me hes going for coffee?

becca x