Forcing myself to eat

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I have absolutely no appetite at all right now and it feel like every time I eat anything I'm having to literally force it down cause i don't even want to swallow the food. Take today for instance i had a handful of sweet popcorn and some mini popadoms at stupid o clock this morning (midnight to be exact) so i could take my medication and then i didn't eat again till gone lunchtime and even then i knew i had to eat but i really didn't want to so i ended up with 2 wraps, some ham and mustard and half way through the 1st 1/2 of the wrap i was full! But because i know i won't eat again now till gone 10pm i forced myself to eat it and now i feel sick. It's so frustrating cause i see my personal trainer twice a week, i go swimming and i walk everywhere unless i have to drive cause of distance and yet i'm STILL not hungry! My trainer has told me to stop logging on here for a few weeks and hand write down EXACTLY when i'm eating and what i'm eating to try and see what is going on. I am also having a colon-o-scopy on the 16th and a test where i have to drink some foul liquid to see how long it goes through my system because i also don't go to the loo like at all really. Bit too much information for people here but most people go like 1-2 times a day right? I'm lucky if i go once a week! It's getting really irritating as well because if i have a few days where i can't stand to eat anything they are then followed by a few days where i can't stop eating. It's just grrr!