These two stories are very similar to my experiences.
To the authors of 'Butt Plug First Time' and 'A Boy and His Toy,' welcome to the club! Keep it up and keep it in! I have enjoyed my variety of plugs for many years now.
As a teenager, I first discovered the extra pleasure of having a thumb in my rear pressing against my prostate while stoking my cock to an incredible orgasm. I somehow found a cigar tube, experimented with that as well as a wooden dowel.
Once I was older and living alone, I acquired a finger-sized plug. This slipped in easily, and I would often shower with it in place. Later, I bought a longer and larger plug (five inches long by one and a half inches diameter) that, when properly lubed, I could accommodate. I also got a similarly sized version that vibrated. It was AC-powered so no batteries wore out. A friend gifted me with a seven-inch 'tool,' a phallic-shaped anal dildo with a flared base.
With enough stimulation, I have had two of my toys inside me side-by-side.
I wish I had discovered anal douching earlier. I have a large red rubber bulb with a slender nozzle attached for this purpose. Anal stimulation often leads to expulsion of fecal material from deeper in the rectum and some soiling of the plug. If you clean your anus and rectum by squirting in water through an enema nozzle and then expelling it again, you'll feel more relaxed and you will be able to accommodate larger objects.
I have experimented with cucumbers, zucchinis, and even sweet potatoes. The largest I have taken in was seven inches in girth and six inches deep. Apply lubricant to both your anus and the object. Zucchinis are often curved and easy to press against your prostate.
When I'm really stimulated, my anus demands to be filled. I have used a lubricant bottle and a shaving cream can as anal dildoes. These are too hard and may have rough edges.
So I graduated to a large, black, latex, seven-inch plug after examining other large dildos. It is smooth and pliable with a suction base. I definitely know it is within and filling me. I enjoy watching it enter me with a suitably-placed mirror. A goal will be to be able to sit or walk around with it inside, as I can with my other plugs and dildo. Indeed, I once slid in my five-incher and drove for several hours while stroking myself.
Happy stroking! Maybe an understanding partner will help you with your stimulating activities both front and rear.