Need some good advice here on OPK?

my husband and I are on our 9 mth going on 10 mths of TTC. I have an 18 mth old and have had 2 m/c since he was born. I have not used a OPK yet. If I do not get my BFP this month I want to try the OPK ( ovulation predictor kit) next month. I live in Canada and want to know what a good brand is to use? It would be much appreciated.