I hope you don't mind me butting in here.........
The fact that you got a 50% line probably means you're headed toward your LH surge, meaning ovulation is just around the corner. I would make sure you have your BD bases covered since sperm last for days in there, it would be a good idea to have some "on board" so to speak just in case, cause you can't always be sure when that egg is gonna drop!
When I start OPK'ing, I usually buy a batch of cheapies from the internet and once I start getting a bit of a line on them, I start using them every pee for a couple of days..........I have never missed the positive since I started doing it this way. I'm too cheap to pay for digitals since they cost SO MUCH here in Canada.
best of luck to you........I hope you don't mind me injecting my opinions, I'm not a usual poster here but since so many boards have gone private, I find myself roaming everywhere looking for people!