My God, PG, I feel you with every fiber of my being!! Grass is the WORST. And it's sooo irritating because most of my family does NOT have this problem, so of course they seem to think I'm being over-reactive about it. My mom, when I was a teenager, didn't believe my allergies were nearly as bad, so I still had to mow the lawn, and when I'd be in tears, red eyed, sneezing so much I couldn't see straight, she'd get annoyed and take the lawnmower stating how I was taking too long.

Luckily my husband has seen me have one of these attacks and won't LET me mow the lawn. As is when I go out to do any weeding or garden work I still have problems, but it's not nearly as bad when the grass is being clipped. I had a few classes in college where on nice days we'd all opt to go out and do class on the grass--and because of course, I hadn't prepped and brought a blanket as a nice barrier, my legs would get a nasty rash from sitting in the grass.
I had one year when I was going between the North part of WA to the South part of WA where the pollens vary greatly, that I ended up trying seven or eight different medications and nothing worked (it was also at the time that they were strictly limiting certain medications in this state due to them being ingredients in meth, so I couldn't buy more than two different meds at once.)
Benedryl worked when I was younger, but right around college I think my system just overrode it..the only time I'd actually NOT have problems with allergies would be when I'd be falling asleep due to the side-affects, but the minute I'd wake back up, boom, the allergies would be back. Tylenol worked as long as I took eye-drops (visine was ok, but there was another prescription strength brand I liked a bit more) and nasal spray on top of it. But when I was pregnant all three became no-nos, and I was left with *one* option, chlortrimaton (well, the generic version), I was actually surprised that if I took it daily, in the morning and in the evening, I had close to *no* problems, occasionally having to take eye drops.
My allergies have given me a new *blessing* though as of August of last year, they've swollen the tubes in my ears that let the natural fluid drain from your ears to your sinuses. So I've had fluid in and out of my ear, causing pressure problems, headaches, etc. Just got it checked out last week, and I've been switched *again* with medications, taking the generic version of Claratin (which...didn't work when I was in Bellingham, but it works here o_O) and a steriod-antihistimine nasal spray.
So far, it's working...here's hoping it stays that way! I hear they have a shot they can give allergy sufferers like us that is an annual shot, but you have to go in and get allergy tested first. I'm sure that once I'm done having kids, that's the first thing I'm going to do

Living in a state that is green ALL year long (including the grass, grah!), getting acclimated has *never* worked for me, in fact, the more I spend out in the grass, the worse my allergies attack (From May to August, some years September)...if the option is open to you, go to a doctor, get it fine tuned to make sure it is grass (even though I know mine is grass, you know yours is grass, the doctor's always want to test to "make sure", since they won't prescribe anything if it's for the wrong thing), and then from there see what's open to you option wise.
Otherwise, yeah...sleeping on your back, head tilted up so your sinuses won't dribble out your nose is...eh, one option ;P