Thanks for using the HCM.
Erection and ejaculation are maintained by 2 different kind of nervous system. So if the sticky liquid is proper ejaculate then weakning of erection is normal because other type of nervous system is activated(PNS). You can give some days rest for it to be normal. Pain in testicles if it is more or severe it may be due to injury
or may be infection. If it continues consult your doctor for detailed examination and further management.
Hope I have answered your query. If you have any further questions I will be happy to help. Thanks get well soon....