You cannot have a positive pregnancy
test through HPT conclusively until three weeks after ovulation and considering the fact that you had the implant removed only three weeks ago, it seems more likely that your period could be disrupted owing to the hormonal
disarray caused. You can get the serum beta-hCG
titre estimation as evidence for exclusion/confirmation of pregnancy. This is an earlier and better way of diagnosis. You should also get a physical evaluation along with a trans-vaginal sonogram to clarify and aid the situation. Hope you find this information helpful. Take care.