The scores on your first few practice tests aren't necessarily great indicators of whether your prep has been effective. The deeper issue is whether you feel as though you're cultivating effective strategies for grappling with GMAT problems. When you work through quant questions, for example, do you feel as though you're grinding through a lot of tedious calculations, or are you effectively using strategies, such as back-solving and number-picking? When you evaluate sentence correction problems, do you remember to consider logic and meaning in addition to elements like parallel construction, modifier placement, etc.? When taking exams do you have effective strategies for dealing with timing issues, should they arise? If the answer to any such questions is "no" you'll want to address those issues before taking another practice exam. If you feel as though you are internalizing effective strategies, then keep going through the 60-day plan, make notes to yourself about what you can improve, and expect that, in time, you'll start to see greater consistency on your practice exams. In the meantime, make sure you're thoroughly dissecting all old practice tests - anything that isn't 100% clear, post here.