No way he is not ready although he may think he is lol. I wouldn't worry if he is only 4 months he's just going thru the motions.
Can My 4 Month Old Male Get My 2 Year Old Female Dog Pregnant?
After your male crosses 8 to 10 months he can mate your 2 yr old female...No prob when I found the same situation with my dogs...the result was normal and fine...Good puppies were born....
Can my 5 1/2 month old Bichon Frise pup get my 19 month old Bichon Frise bitch ( already in heat ! ) pregnant? He has tied 3 times in as many days and they are both desperate for each other.