First the count 70m/ml is normal.but the progressive sperm count
I recommend you to visit a general surgeon
who would examine your testicles and advise you for a semen culture and a doppler ultrasound
of the testicles as required.
The doctor may advice you a short antibiotic course.
In the meantime you should wear loose underwears and take a brisk walk of 30-45 minutes each day.
Second pregnancy involves a number of factors.4 months is ni time.
If after 8-12 months of unprotected intercourse
,your wife does not conceive,a doctor shoukd be consulted for investigation.