pimples on penis shaft

Hello, well ill try to get stright to the point, i have had these pimples appear on my penis shaft for more than 2 years now, i have been to my doctors twice and they say its a blocked gland, but as you can see they are still here after 2 years, i noticed the first one one day after unprotected sex, but i was reading some stuff and it says std/sti dosnt show anything untill like 2 weeks after, well anyways when the pimple appears i try to pop it and sometimes puss comes out or nothing comes out but when i try to pop it, it gets bigger, but then it will go away like 3-5 days later, then about 2 days later i would get a new one, they dont hurt unless i try to pop them, i have two of them at the moment, i poped it and blood just came out then a day after i poped it again and puss came out, i really dont know what to do as i have already been to the doctors twice please help :,(

---Jamie