u have to write down or make an analysis what u dun trust about your partner or is it you're too sensitive and dun have confidence in yourself first?
Could be that u feel insecure eveytime she for e.g speak on the phone to another 'guy' friend or wear sexy clothing going to uni/work, etc.
make a note man what u dun feel good what u dun like her to do that makes u lose trust.
Figure out whether is she cheating on you that makes u lose trust or is it just her real character like that for e.g is she always flirty/cheeky when she talks to ppl (maybe it's only natural that she was brought up to talk to ppl like that). If that's the case then u know that she loves u and she's just being herself, nothing much to worry. Sometimes u gotta let her go loose, dun hold on too tight man, you'll suffocate her. Maybe let her go with her friend (can start off with just girls only) depending on your jealousy level hehehe for 1 night then when u feel more confident maybe let her go out with a group mix guys/girls, etc.
I think the most important thing is that trust dun come so fast can take a long time but u can develop and start now. Start off by letting her do what she like not what u dun like her to do. But judging by your post, seems like u already got an issue with trust

with your partner so I think just let her do wat she wants now, dun fight it, girls ah always want to win wan hate to admit they're wrong so just give her space now.