Fixed-Dose Combinations (FDCs): Medicines are discovered individually and are supposed to be taken separately. A huge number of irrational, illegal combinations of drugs are being sold in India; quite a few without mandatory approval of the Drugs Controller General, India (DCGI). Except in a few cases (such as TB medicines), it is always better to take medicines separately so that dosage can be adjusted and side effects monitored.
You case illustrates the dangers of taking combination medicines such as Amlobet that contains amlodipine and atenolol in one tablet. Had you been taking the two drugs separately such as atenolol (Brand names: Aten, Tenormin etc) and amlodipine (Brand name: Amlodac etc.), you would not have taken all the tablets twice even by mistake. Headache and sweating are the side effects of overdose but fortunately will go away. However in future you should take the two medicines separately. You did the right thing to drop a dose but the answer lies in not taking overdose.
I am a little bit concerned that at the age of just 37 years, you are taking three medicines to control your blood pressure. It is now established that when more than one medicine is needed, one should always be a diuretic - that reduces the volume and reduces the need for strict salt restriction. I should think that a long acting, low-dose dual-action diuretic such as indapamide (Brand name: Indicontin Continus) and amlodpine (Amlodac) 5mg a day should control your blood pressure. If not, and then only, should one think of using three medicines.
It would also be very helpful if you do brisk walk for 45 minutes (to cover not less than 4.5 km) a day.