Medication sometimes constipates me and I have Movicol sachets if it gets too bad.
You would be better off by eating one of the oranges instead of drinking the juice as all the roughage is in the whole fruit, not the juice.
Try not to eat too much red meat. If you like fish, the fibres are more digestible than meat. If you eat potatoes, try and eat the skins as well, so if baked potatoes are on the menu, opt for that. The skins contain the majority of the vitamin C and all the roughage. Fruits with edible seeds, such as strawberries, raspberries, etc, will all help. If eating apples, don't peel them. As already mentioned, sweetcorn is a good bet. I know that you mention flatulence, but if you can eat baked beans, broad beans, that can help as they're cooked with the skins on and will help with more roughage. Once your bowel gets back to normal, you can eliminate any food which you prefer not to eat.
You must drink plenty of water too, especially if your job makes you sweat to a moderate degree. You need to replace the water sweated out plus enough to keep your body hydrated.
Hope you feel better soon, I know how uncomfortable this can be!