I am really confused if my girlfriend is cheating or not please help?

I have been with my girlfriend for over 1 and a half years know we get along together really well, but my gut tells me there is something not right about her. for example we live in a flat with 2 other guys and sometimes when i come home from work i get the strangest of feeling especially when i walk through the door and i say hello and i get a delayed responce and i see my girlfriend ironing but one of the guys is stood right next to her and tries to creep away from her to the other side of the ironing bord and tries to tell me hes teaching my girl how to iron when i know perfectly well her mother tought her how to iron also the look on her face was a very surprised look. another time was i was looking on my computer while she moved to a position to make me think she was looking to but infact when i looked she was looking at him and he was looking at her and as soon as he realised i was looking aswell he turned away extremly fast as though they where having a little through looking at each other also sometimes when i look at her phone she grabs it from me and asks what i am doing. the only time i can look at her phone is when she has gone through her inbox and outbox and i can see that there is no messages on her phone from upto 10 days ago and her recent contacts he is one of them. she tells me she loves me all the time but it just doesnt feel right. also he cooks for her aswell and now as soon as i come home from work he goes straight to bed like he does not want to be around me or is guilty. but he is always around when its just her in the flat. i spent 2 weeks at her mothers house while she stayed at the flat and on her days off she would not even send me a txt message or call me until she was just about to go to bed. when she came to visit at her parents house she waxed everything her her armpits and her legs i asked why she was doing it and she said it was because she did not want her colleges to see she was hairy. but what got me is why would her colleges look at her virgina or her legs when she only wheres trousers at work also alot of the time when i tried to seduce her in bed she would just laugh and turn away and say she was tired but only untill i said to her why does she do this she started having with me again but then it stopped again and now she has a urine infection so she calls it. she says her vaginer is burning. i know i have no std because i got checked 3 months into the relationship and she only had with one person before me. and also it used to be tight to put 2 fingers inside her and now it is totally loose i could put 3 fingers inside no problem so it makes me think if this guy is alot bigger than me downstairs. and i am not the biggest in all counts. Also she seems to be very tired everyday when she comes home from work unable to have just to cuddle, i work 17 hours per day and i still have the energy to have a little fun with her if she would let me. She never lets me go down on her either her excuse is that it tickles to much witch is bullshit because we all know every girl loves it when we go down there to give oral. I love my girlfriend more than anything in the world but my gut keeps telling me something is not correct about her and him and makes me think he is a better lover and her dirty secret. And also i have never met a women who will never argue with me she always does things for me and does not moan if i dont clean or anything is that a sign of guilt? i just dont know. anyway thankyou for spending your time to read this and i hope i recieve a reply