Sorry for the novel but i'm confused....quick advice please?

I'll try to sum this up as best as possible....I'm dating a Doc student who is divorced, over year and half now, and in the beginning (week into it) relationship was bliss. about the second week, things changed and I noticed (or felt distance) between her and I, no worries just htought it was me being too sensative. the week before Vday someone sent her a fruit basket at work. No worries on my end, but she was pretty bothered by it and wantd time alone? telling me that since she met me guys were coming out of the wood work approaching her and she wants to make sure she is making the right decision. (wtf???) So anyway i communicate to her that i'm botherd that this is bothering her.... so time progresses, and the sunday before Vday i try to surprise her by popping up w/ flowers. it was around 9:30pm. she wasnt home (not like her btw bc she studies alot...so i think). so i drop off the flowers w/ a note and called but got vm so i lft her a mssg. then sent a text.... no response.... hours go by, well pst midnight still nothing... .so i go by her place only to notice everything is still the same she never been home.... i'm worried now...things going through my mind.... the nxt day (vday) she wanted me to pick her up at work and not at her home???.... so i did... noticed immediately that her hair was all over the place and her clothes lookd as if they were thrown on w/o much care.....and she looked very very tired..... the day progressed well as i processed everything that went on....at the end when i dropped her off i tried communicating my concern to her and i note the way she is dressed as affirmation of my concern ( or to validate my theory that she did not sleep at home)....i used the word un kept which apperently offended her, but no once did she answer my question.....ne way later on that day she told me she needs time to be alone. i told her i respect that....couple days go by not much convo, but later that evening we talked via text about the song that i wrote to her and how she wanted to hear it "one day" but she also stated to me how 'things would be easier if we lived together and i was coming home...but that's not the case".... i responded how we should take it one step at a time and we said goodnight....anyway the week progresses and not much convo between her and I....and on Friday and saturday i made an attempt to go by her house late (again around midinight b/c i have been having this feeling) and what do i see? she never was home...at all. which only confirms that she been sleeping somewhere else.... let me also note that i have made several attempts to talk to her about this w/o pointing any fingers or making judgment calls. I told her how i want us to be Open and honest in how we communicate (b/c i have been open and honest the whole time we've been dating)....she keeps telling me that it's her schooling studying for her PHD and working fulltime which is why she has no time for me.....and though i do understand that getting a Phd is no cake walk aswell as working full time on top of that.....but what does being gone all night have to do w/ it?? .... i didnt say this to her of course b/c after the incident on Vday.... i've been rather reclusive and kept my comments and concerns to myself to try and keep the peace, hoping that, if infact she is being untruthful, she will soon tell me..... but guys i don't know what to do really. thanks for ur help