Why Beta hcg elevation in non pregnant?

Proper periods on June 3. Protected intercourse using condoms on June 11. Took no ipill. Was worried so much. Expected periods on July 3 but delayed. So beta hcg on July 6, result was 0.63. And took primolut n to get periods for 5 days and got periods on July 14 but the periods was VERY LESS. so took beta hcg on july 16, result was 0.244. Still had confusion, so took beta hcg on july 31, which was 50 DAYS after INTERCOURSE. The result came out as 2.1 miu/ml. Since the result was 2.1 I took another test on the same day in different lab, the result was 0.60. Why I got two different on the same day? Took scan on july 20, but not informed about intercourse, found cysts on ovary, so suggested krison 35. May I know why did my hcg levels raise from 0 to 2? Is there any problem? Can the pregnancy go undetected even after 50 days? Please help me. Is 2.1 miu/ml is very high? And is there any chances of pregnant?