We call them 'guess-strips', for a reason. (Actually, my experience with pool test strips has made me nervous about the fact that similar strips are used medically. It makes me wonder how often they are validated!)

You need some CYA. If you have access to a Sams Club, check and see if they sell "PoolBrand" dichlor shock in a 24 x 1lb box. Most do; and at a very good price. The bagged shock in that brand is undiluted and unblended (good!) -- each bag will add about 4 ppm of chlorine to your pool, but also about 3 ppm of CYA. By the time you've used 2/3 of the box to chlorinate, you'll also have a good CYA residual.

If you can't get it at Sams, you'll probably need to order online. Walmart, Costco, Kmart and most pool stores are selling a blended mess of dichlor and other goop. Lowes and HomeDepot vary by location, but you'd have to be an expert label reader to get the right stuff IF they have it. This product from Amazon is also unblended dichlor:
Kem-Tek Dichlor 22 lbs