I'd go to the doctor's - I have suffered for some years. I have a nasal spray, and a daily Cetirizine antihistamine tablet, and anithistamine eye drops. I haven't found anything over the counter which works as well.
MSM tabs - get them from a health food shop or online. Start with 1 a day and increase cautiously until you find your ideal dose. I can only take 2/ twice a day, or I get headaches, but worth persevering with because hey, no hayfever!
Methylsulfonylmethane. Some people may have the luxury of thinking it's stupid, but then maybe they are not disabled by the horrible symptoms of bad hay fever. It works for me BertiWooster, makes the summer a whole lot more bearable, it may not work for others. I have also heard that if you eat locally produced honey prior to the hay fever season it can help. Bit late for this year now though.
There are other things you can do to minimise pollen intake. Cover your hair when you are out. Wash hands and face often. Drive with the windows shut. Dust with a damp cloth and Hoover often (sorry) change clothes on arrival home (shower too if you can) keep your outdoor pollenny clothes out of the bedroom. Wear sunglasses. A little Vaseline round the edge of each nostril if you can stand it traps some pollen before you can inhale it. Wipe it off and renew often.
Local honey works for me (1 teaspoon a day). If you do try this keep in mind that the first day you take it your hay fever goes mental but then it works a treat.