Sickness and diarrhoea are not always caused by food poisoning and food poisoning isn't necessarily the result of the last thing eaten. A lot of food poisoning bugs incubate within your system before symptoms become apparent. The time scale can be days or even weeks according to the type of bacteria involved and to a certain extent, the ability of the individual to fight the infection off. In those instances, the predominant symptom is diarrhoea because that is the most direct route for the body to rid itself of the infection (apologies if you are eating your tea whether home cooked or via Just Eat).
Some organisms can produce toxins on foods such as Bacillus cereus which is commonly associated with cooked rice that has been subjected to temperature abuse after cooking. If foods containing this preformed toxin are eaten, the body detects the the toxins and the initial and predominant symptom will be vomiting fairly soon after eating (i.e within hours) as this is the most effective way of removing the toxin from the body.
As someone else has already said, there are other things like viruses eg Norovirus that cause D & V symptoms and this is rarely connected to food (but not impossible). Viral symptoms tend to be violent from both ends.
If you believe that your symptoms are food poisoning, in the first instance you should go to your doctor and submit a faecal specimen that will be sent to a microbiology lab where it will be examined for the routine food poisoning bugs. If anything is identified, your local Environmental Health department will be notified by the lab and they will follow it up by contacting you to get more information on your food history. Unpleasant though this is, it is only way of either confirming what the infection is or it will rule out food poisoning.
You can also contact your Environmental Health department directly and alert them of your concerns but you will need to give them the details of the takeaway (not Just Eat) where your food came from and exactly what you ate. EH may not visit the takeaway purely on your report but if it is somewhere there are already concerns about and also if you get a positive result from your specimen, they almost certainly will visit.
You can also check the food hygiene rating of any business that provides food on the Food standards Agency website at
www.food.gov.uk .