“Eman is to believe, even when an overpowering tide of evil surrounds you.” –Imam Anwar al-Awlaki
Remember, Allah controls eman. Even great Muslims sometimes die as disbelievers, wa iyyadubillah. O Allah, protect us from that evil end.
Among the many means to strengthen include constant rememberance of Allah and reminders of the hereafter. Ask Allah to strengthen your eman, and inshaAllah even your low-points become higher and higher over time.