I've never used OPKs, but my favorite pregnancy tests are the ones from the Dollar Tree. Can't beat $1 for a pink dye test! It is a dropper test, so maybe buy a mug while you're there to pee it (and keep it away from the kitchen ). I never got anything but very clear negatives and very clear positives from my many months of TTC DS. I got lots of evaporation lines from internet cheapy dip sticks though.
I need to get some new OPK's but I have a stash of about 50 IC HPT's I got on Amazon.
I have clearblue easy digital opks & wondfo opks/pregnancy tests which I ordered off of amazon. If you are a student make sure you sign up for amazon prime because you get free two day shipping for a year.
I was going to suggest Wondfo as well, I've never used them but I know a lot of women love them. I get mine from saveontests.com because they are a Canadian site so they have the best/cheapest shipping options to Canada (their shipping to the US is super cheap too.)