Hello lexxipexxii thanks for your question Dizziness, weakness, fast heart rate is common during menstural cycle. There might be many reasons as - It might be due to deficient iron in blood. Low hemoglobin or anaemia may present with palpitations and weakness and its a very common problem in young females. So what you can do is get your Hemoglobin levels checked and if its in lower range then start taking iron supplements. - Second possibility may be Dysphoria due to menstural cycle or also called as Pre Menstural Dysphoric Dysorder, its a disorder which usually manifest as change in behavior, anxiety, irritability but in some case may present as panic like increased heart rate, weakness, headache, shortness of breath. You can take low dose clonazepam for this (after advice of doctor) or you can try light exercise or yoga for relaxation hope I solved your query Thanks take care