According to the data you provided (spotting after changing from acnocin to diane 35 birth control pills, having unprotected intercourse, noticed external swelling at the stomach), you might be experiencing spotting due to hormonal blood level changes.


Both Acnocin and Diane 35 contain the same generic active substance (cyproterone ethinyl estradiol). Therefore, the bleeding that is expected when changing from one birth control pill to another cannot explain your bleeding. More likely the reason for the bleeding is the improper use of the birth control pills.


Birth control pills containing cyproterone and ethinyl estradiol are recommended to be taken in the following regimen: taking tablets containing active substance for three consecutive weeks and then taking tablets without active substance for one week in which a period is expected. Certain manufacturers do not put inactive tablets and recommend not taking tablets for one week after the third week instead.


Anyway, bleeding during the three weeks when you take the active pills is not expected and if bleeding occurs a visit to gynecologist is recommended. There might be many causes for the bleeding, including temporary hormonal blood level changes. Sometimes the birth control pills cause the changes and need to be replaced with other pills. Conditions like cervical polyps or uterine fibroids might cause the bleeding, too. To rule them out a physical examination by a gynecologist is needed.