help with sewing?

i am a newbie around a sewing machine and so have only made a few bits, so far without a pattern just cutting around existing items. am learning lots just by my mistakes. have so far made pjs for ds1, nightie, 2 satin pj tops and a pair of palazzo pants (far grander the title than they are) anyway that gives you an idea of my limitations. i was a bit hit and miss with the pants and so they have turned out not fitting. the length is fine and the waist is fine (elasticated waist) only problem is wedging them up and when i get there they are super fitted around the stomach bit. way too much even for a baggy top to cover, but like i say the waist is fine. was just going to stick them in bottom of material basket and hoped to fit in them in time, i know thats not going to happen. so, i am teaching myself sewing for the very same reason to adjust my clothes but know nothing about it yet. was considering putting a kind of v shaped material from the crutch to waistband back and front or would it be better to put the v in the sides......can anyone help please?