Lag spikes during autosave and just in general whilst placing blocks and breaking blocks and handling crops etc.

Placing blocks, breaking blocks, crops etc will occasionally cause them to not break properly. In the case of non-crop blocks, when you attempt to walk through a block you just mined it'll push you back like it's an invisible trampoline until you place the block you just broke. Which will then appear as if you hadn't broken it yet. Additionally, huge lag spikes whilst doing non strenuous GPU things. I am playing with 2 mods, minecraft classic texture beta, and the tree capitator add on from Marketplace. The lag spikes existed before as well as the block issues a couple updates before the latest one. Please fix this as I'm afraid to lose my stuff to a mob due to lag at the wrong time! Thank you :3