Curious to know if my birth control (dasetta) will be less effective because i'm taking doxycycline?

No.: your birth control will not be affected by the use of the antibiotic, doxycycline. Perfectly safe.

Effectiveness of BCP: It could be less effective . I would recommend a back up like condoms for the rest of the cycle.

Yes: Antibiotics can decrease the of birth control and if you need antibiotic therapy you should use a back method of contraception when using antibiotics. You can always abstain from intercourse while on antibiotics.

Antibiotics and BCP: Antibiotics may interfere with efficacy of BCP's. So you should use an additional form of birth control while you are on antibiotics just to be safe.

Drug interaction: "Antibiotics such as doxycycline may reduce the effects of ethinyl estradiol in some women. If you are using ethinyl estradiol for birth control, you may be at increased risk for pregnancy or breakthrough bleeding." (http://www.drugs.com/interactions-check.php?drug_list=940-0,1044-15529)