So my baby is 3.5 months old and can do mini push ups and roll over BUT he can only do them if I prop him up on his arms. He won't put himself in the position to do them. I'm wondering if I'm helping him by putting him in the position, i.e. teaching him, or am I hindering his progress?

It's great, it helps build strength

 

I wouldn't do it. He will roll when his arms are ready to hold him. You aren't helping him, you are forcing him. Let him go at his own pace, he'll get there.

I might do it once a day, just very briefly, but then let him go at his own pace. He'll be rolling over before you know it. :)

Who told you a 3 month old can do these things? Stop forcing him to crawl.

He sounds right on target. Don't worry about crawling; it's not a milestone and many babies never do it.

Just do tummy time however you normally do it; he'll take it from there.

All babies move at their own pace. Don't force him to do anything he isn't ready for. My son never rolled over or anything and he crawled at 7 months.

It is perfectly safe as long as you are there to help and support him. My child had physical therapy at 10 days of age for 2 years at a highly successful and well qualified private center. I can't tell you all the positions they were putting him in so that he would be able to start bearing weight and be able to get into the correct patterns for movement. He did great. But the key is not forcing the baby into any position that is not natural, and being there to hold and support. That said, babies do crawl when they are ready, but there is no harm in helping to build some of the strength and muscles that it takes for that to begin based on my experiences with the professionals. Since my first one, I have done this with all my babies. Tummy time is the most important thing you can do, and getting him up on his hands and knees definitely will not hurt. Also, crawling to the professionals is critical for development, don't skip it!