Sounds like allergy triggered asthma. I have that too (as well as exercised induced asthma which sucks...). Feels like you are breathing through a straw, and maybe noticing some wheezing in your lungs at times (or coughing)?
In addition to some of the suggestions, some techniques I use for the asthma is controlled breathing (slowly breath in through your nose as deep as you can, hold for a couple seconds, then slowly exhale through your mouth). That helps train yourself to take deeper breaths than normal when your lungs start restricting which can help.
Since your doctor indicated it's related to your allergies, make sure you are taking whatever allergy medication he prescribed. If he didn't prescribe any, I'd recommend trying the OTC (over the counter) Benedryl allergy medication - as it's designed to control common allergies and when it was still a prescription drug, was the "go to" drug for asthma attacks. I only use this one when I feel an attack coming on - not something to use like vitamins. If you have never used OTC allergy medications, I'd recommend picking a small packet of one brand and try it per directions. If it seems to reduce the allergy reaction, stick with it. If not, try the next one on the shelf. Once you find one that works for you, note the active ingredients used - as those are the drugs that work for your body chemistry/allergen reaction. What works for one person may not work for another. Knowing the active ingredients helps when medicines change over time or re-branded - that way you can choose another brand that uses similar compounds to cut down on trial/error.
Also, if you haven't been tested - you may want to look into taking an allergy test to find out what you are allergic to. I know ragweed season is closing in on us (depending on where you are in the country) - and that tends to be a typical nasty allergy many suffer from. By knowing what you are allergic to, you can monitor pollen counts or activities you do which put you into close contact with the allergens that impact you - so if you start feeling your asthma getting worse, if you know you've been around your allergens - you can probably deduce it's your allergy acting up and take whatever action you need until the attack passes or allergy subsides.