Here's some advice from an allergy veteran--50+ years of sneezing, runny nose, itchy eyes, etc.
1. Allegra and Claritin have different modes of operation, according to my allergist. So, you can safely take both at the same time and you won't O.D.
2. When mowing the lawn, use a pollen or dust mask, and maybe safety goggles, the kind that wrap around and just about seal your eyes from all sides. Then rinse your face after you finish mowing and maybe even change your clothes.
3. Get a Neti pot or a Neil Med sinus rinse kit. The kit, you can get from Costco for a reasonable price and it's got enough saline for a season. It's gross, but you use it to rinse out your nasal passages. You will be amazed at how well it works.
Just for info, pretty flowering plants are NOT the source of your allergies. Those plants are pollinated by insects. It's the wind pollinated plants that are the problem, and they may be filling the air with that nasty stuff at the same time as the pretty flowers are out. So don't blame the flowers.
My allergist told me my allergies would calm down when I get older as the immune system gets weaker. Worked for me, I have a lot less trouble now that I am in my late 60's. So, take hope, in a twisted sort of way.