LDR issue need help ASAP

Hello
I have no idea how to say it but here it goes. i am also thinking to see a specialist if there is a need. i have been in a LDR for 3+ years. i know its hard no doubt but we both respect our needs and the reason to why we need to be apart . she may come to me after her studies, not sure . we are in it for a long haul(if there is at this point). we are both Emotional and sensitive. so it hurts when something like this happen. i dont want this to happen anymore i do anything. just got lost here for solution. things were working so fine she was trusting me and caring me( and start loving me from far distance and same for me as well). then we decided to get more serious last 1.5 . we live in a different Countries and she went there for school. last year after i completed school (after 3yrs of not seeing each other) i decided to join her for a holiday 90 days and we were both excited. she cares for me and we both love each other and we are taking our time to decide for our future( no expcetation from any part). Recently i have been doing some stuff (more than once) that got her upset and she does not surprises like that ( i help a friend Female with her divorce and she end up having feeling for me even she knew i am not into her and working on my current GF ( wrote me SMS ) but my GF did not(about the feeling part only) ( i told her a bit later when i meet her in person when she read a SMS she got so upset and shocked and said why i let her become so close to me and did not control it and did she know about me. ( she even talk to her on my back) so we talked and things got a bit better but the main thig is that she does not Trust me anymore and she keep telling me i dont care about what u do ur keep lie to me i know it . i was just helping my friend thats all. but now i am back and really dont know what to do . i really love her and want the best and i know she loves me too but with the current situation and long distance what is the best solution . how can i gain my trust back. i know it takes time but i need to tell her sometihng so she wont leave me.( i gave her space so she could think and dunno do the girl stuff thing) ( FYI she's my first)
i promised her that i wont deal with my firend anymore and be honest with her and tell her everything even it may hurt( even i told her my reason but she think its all excuses). i think because of the trust issue she does not believe me and think i am doing something on her back even though she know i never do. not sure what i should do ( i apologize but its not enough i know i need some action plan. please response if anyone need more info i will tell u .

how much time i should give her to think about it one week few days??. i will call her to explain and email her my decision and apology) its sucks cause valentine is on the corner.

we are in both mid 20s