Hi,
It's not uncommon for women to experience cramps and other period-like symptoms even when they're not menstruating. There can be a number of reasons for this, including 
hormonal imbalances, stress, changes in diet or exercise habits, and other medical conditions.
In your case, since you haven't had a period in three months and have had negative 
pregnancy tests, it's possible that your cramps and symptoms may be related to hormonal imbalances or other issues related to your 
hypothyroidism. Hypothyroidism can sometimes affect menstrual cycles and cause 
irregular periods or other symptoms like cramps and 
bloating.
Starting birth control can help regulate your menstrual cycle and may help trigger your period, but it's important to continue monitoring your symptoms and discuss any concerns with your healthcare provider. If your symptoms persist or worsen, your provider may recommend additional testing or evaluation to rule out other potential causes. Additionally, they may want to adjust your medication or treatment plan to better manage your hypothyroidism and related symptoms.
Take care. Hope I have answered your question. Let me know if I can assist you further.
Regards,
Dr. Diwashish Biswas, Internal Medicine Specialist