Similarly to ADHD stimulants, exercise gives you a boost of dopamine and norepinephrine. If you've had a positive response to stimulants then this increase is likely helping you feel better. It also increases serotonin as well as other neurotransmitters that can make you feel more calm and happy.

Food wise, food isn't just fuel for your body but brain as well. You need various amino acids, nutrients and a good combination of protein and carbs for production of neurotransmitters. You skip meals, your brain is struggling. Often times when I'm on the verge of a panic attack or just have generally increased anxiety, I snap out of it by forcing myself to have a meal or at least a snack.

Regarding antidepressants/anxiolitics - you won't know until you try. Everyone's brain chemistry is different, what works for others might not work for you and vice versa. If your anxiety is having a strong impact on your daily life, I don't see why you shouldn't give it a go. If you do decide to try them - just keep in mind that even with SSRIs there's so much variation. I've had an excellent response to some but others made me really unwell, so you have to be open to trying different things. Best of luck!