My girlfriend can't orgasm ?

Hey everyone sorry about the spelling but I'm on my phone, my gf and I enjoy sex very much but are getting frustrated with her inability to orgSm, I can last as short or long ad I wish(lasted as little 15 minutes and as lOng as 2 hrs) and I have made her orgasm before but only by prolonged oral and/clitoral stimulation, i have never ever had issues giving sexual partners multiple orgasms just by having sex but her I can't get off without manual stimulation for a long time, I have tried multiple angles, thrust power, speed, duration, patterns and still nothing....plz if u have any suggestions I would appreciate it, we have been actively havIng sex for , months now if that matters, plz help!!!