There are many types of blockages that can cause vomiting, Hazel.
Firstly, it can be a food obstruction due to eating something very hard to digest, fibrous or thick things like potato skins. Secondly, it is because there can be swelling or narrowing of the intestine somewhere further down (those can be caused by adhesions (scar tissue that winds itself around the intestine), some kind of a thickening of a spot on the intestine so that it is no longer stretchy and won't allow bulky things through or a twist.
Sometimes it is a combination of a lot of those things.
I had scar tissue glue a loop of intestine to the abdominal wall. I could feel it whenever I ate. Some things like mashed potatoes would block up the loop and I would throw up for hours or days. I only went to ER 3xs with blockages then realized that I could help them along on my own by moving, walking and bouncing up and down on my toes...I even bought one of those big Pilates balls that I sit on and bounce gently. It does help.
I have a cutoff time...27 hours. That is how long I will go before heading for ER. After that, I know that it can become dangerous, I dehydrate, can no longer take my meds (dangerous) and that I cannot help myself but need a doctor. I do not fool around with stuff like that.
My only real rule is that when I feel the blockage coming along, I stop eating. At some point, if I cannot even take a pill or sip water, that is my sign of a full blockage. I feel like I am in labor...Waves of cramps that have me screaming in pain.
If I can ride it out for a day, I do. But past 27 hours, I know that I am dehydrated, dizzy and weak. That is when I head straight for ER.
Different people live it differently and have different personal rules. Mine is that I do not take a chance with my guts.
I had surgery twice on the loop. They 'liberated it' but the adhesions come back in about 2-3 yrs. Nothing that they can do about it.
The only advice that I can give is to get to know your body and what it needs then do it.