There are various factors affecting the sperm density and characteristics. If you are having frequent intercourse it may be thin sometimes or sometimes it may be some internal problem too. If its really troubling you, please visit the hospital after the lockdown is over and have the semen analysis and be sure if its normal or something wrong out there. For further opinion with the andrologist please visit this link and have online consultation: https://www.hamrodoctor.com/doctor/dr-amit-kumar-shah/ Thanks!