When doing your splits, here are some tips that might help you:
1. Always make sure that you hold your splits for AT LEAST 30 seconds. I was taught that anything less than 30 seconds is pointless, and the longer you hold it, the better it will be.
2. If you are quite close to the ground (10-20cm away), try not to use your hands to hold yourself up. This can stop you from going down as far as you can. Place your hands on your thigh instead. It hurts more but helps a lot.
3. Try leaning forward in your splits and putting your chest on the ground for 30 seconds.
Other than actually doing the splits, I think the best thing you can do is have someone stretch you. Stand with your back against a wall and make sure you have something to hold onto (like a doorframe or chair). Have someone lift your leg straight up (as if you were going to pull a bow and arrow). Let them push it back and focus on keeping your bottom leg straight. Do that for 30 seconds, then rotate your hip backwards and have them push your leg up more like a heelstretch. Do that for 30 seconds and then switch legs.