Each medication can have side effects. Some side effects can be related to dosage, some to duration of drug use and some can be related to even the mere commencement of the drug. However, the vulnerability to certain side effects can really be accentuated based on underlying physical illnesses or known medical conditions a person is afflicted with. One needs to be very careful about consistent and persistent rise of blood pressure, which itself can be related to many factors rather than solely because of initiation of new medications.
I would suggest a good cardiac work up including detailing of any family history of medical problems - prefer to go to a physician for this. There is always a possibility that the increase could be related to clonil but not very common with just 25 mg/ day dosage. If there is no comorbidity and the blood pressure is still a problem, you may want to discuss with your psychiatrist for a change to other anti - OC medications.